Examtests with Statistical Methods for Psychology by Howell - 8th edition

What are important concepts of research? - ExamTests 1

MC-questions with chapter 1

Question 1

To estimate the percentage of Spanish inhabitants in the United States, we draw a sample from a small town in Nebraska. What is lacking in this case?

1. Internal validity
2. Random assignment
3. External validity
4. Non-random assignment

Question 2

A study is designed to examine the relationship between weight and length. In this study, 20 men and 20 women participate and they men and women are compared to each other. What type of variables are used here?

1. Discrete variables
2. Continuous variables
3. Both
4. Neither

Question 3

A researcher wants to examine the relationship between extraversion and self-esteem. For his study, 100 children fill out a questionnaire about extraversion, on which they can score between 1 and 10. A score of 1 means "introvert". A score of 10 means "very extravert". After filling out this questionnaire, the researchers asks the children to indicate how much self-esteem they have, again on a scale of 1-10. The researcher expects that children who score high on the questionnaire about extraversion, also indicate to have high self-esteem. What is the measurement scale here?

1. Nominal
2. Ordinal
3. Interval
4. Ratio

Question 4

For a research study of the University of Leiden, the BMI of 50 students is calculated. To do so, the weight and length are compared for different age groups. Which measurement scale is applicable here?

1. Nominal
2. Ordinal
3. Interval
4. Ratio

Question 5

Which term is used for a measure that refers to the population?

1. Statistic
2. Parameter
3. Variable
4. Sample

Question 6

Someone claims that the score of Elise on a certain variable is twice as high as the score of Adriaan. Which measurement scale is minimally required to make such a statement?

1. Nominal
2. Ordinal
3. Interval
4. Ratio

Question 7

For a research study, the variable intelligence is measured as follows:

1 = IQ below 70
2 = IQ between 71 and 90
3 = IQ between 91 and 110
4 = IQ between 111 and 120
5 = IQ above 120

What is the measurement scale of this variable?

1. Nominal
2. Ordinal
3. Interval
4. Ratio

Open questions with chapter 1

Question 1

What is correlational research?

Question 2

A researcher wants to examine the extent to which giftedness of children in primary school associates with behavioral problems in the classroom. What type of research is appropriate to examine this research question?

Answers MC-questions with chapter 1

Question 1

C. External validity. The sample does not represent the population well.

Question 2

C. both. Gender is discrete. Weight and length are continuous.

Question 3

B. ordinal. There is a order in the scale. However, there is not a legitimate difference between points on the scale. Neither does this scale have a "true" zero.

Question 4

C. ratio. There are legitimate differences between points on the scale. Yet, there is no "true" zero for BMI.

Question 5

B. parameter.

Question 6

D. ratio.

Question 7

B. ordinal.

Answers Open questions with chapter 1

Question 1

With correlational research, the relationship between two (or more) variables is examined without making statements about cause and effect.

Question 2

Correlational research.

How can data be described and explored? - ExamTests 2

MC-questions with chapter 2

Question 1

Which statement is true?

I. A normal curve takes the mean and standard deviation of the data into account.

II. A kernel density plot takes the mean and standard deviation into account.

1. Only statement I is true
2. Only statement II is true
3. Both statement I and II are true
4. Both statement I and II are false

Question 2

Characteristics of a normal curve are (multiple answers may be applicable):

1. A symmetric distribution
2. A bimodal distribution
3. Positive skewness
4. Mesokurtosis

Question 3

Which measure of central tendency can be used for a variable with a nominal measurement scale?

1. Variance
2. Median
3. Mode
4. Mean

Question 4

Examine the following scores: 11 15 19 26 37
Which statement is true?

1. The median is 19
2. The first quartile is 15
3. The distribution is positively skewed
4. The interquartile range is 26

Question 5

A study is designed to examine the mean IQ of children on a school in Leiden. A sample is drawn that consists of six children. Their IQ scores are: 110 105 80 85 90 100.

What is the variance?

1. 140
2. 10,95
3. 120
4. 11,83

Question 6

Suppose the following scores: 3 4 6 8 19

I. The inner fence is -2 to 14
II. The score of 19 is an outlier

Which statement is true?

1. Only statement I is true
2. Only statement II is true
3. Both statement I and II are true
4. Both statement I and II are false

Question 7

The collected data is multiplied by 3. The old standard deviation is 1.41. The score of Floor is 5. What is the new variance?

1. 15
2. 18
3. 36
4. 45

Open questions with chapter 2

Question 1

After the exam of M&T, we examined for 11 students how many of the 40 questions with chapter they answered correctly. Their scores are depicted in a stem-and-leaf diagram:

What is the median?

Question 2

What is the median of the scores: 4-6-8-10-18?

Question 3

What is the median of the scores: 8, 9, 14, 15?

Answers MC-questions with chapter 2

Question 1

A. A kernel density plot does not take into account the mean and standard deviation, but aim to plot the data with a smooth curve, taking into account that each measurement may have random noise.

Question 2

A and D. Normal curves have a symmetric distribution and tails that are not too thick or too thin. In addition, there are not too many or too few scores centered in the middle of the distribution.

Question 3

C. The mode represents the most common score, which is the only relevant measurement for variables with a nominal measurement scale.

Question 4

D. The IQR is 26 - 15 = 11 (instead of 26).

Question 5

A. The mean is 9, so:

Sigma (X -)2 = (110 - 95)2 + (105 - 95)2 + (80 - 95)2 +95)2 + (90 95)2 + (100 - 95)2 = 225 + 100 + 225 + 100 + 25 + 25 = 700.

700/n-1 = 700/5 = 140.

Question 6

C. The first quartile is 4, the third quartile is 8. The inner fence lies 4 x 1.5 = 6 points above the first and third quartile, thus it runs from -2 to 14. Score 19 is then an outlier, because it lies outside the inner fence.

Question 7

C. Variance is: s² = 1,412 is approximately 2 and s²_new = 32 x s²_old = 9 x 4 = 36

Answers Open questions with chapter 2

Question 1

19

Question 2

8

Question 3

11.5

Why and how is a normal distribution used? - ExamTests 3

MC-questions with chapter 3

Question 1

Which statement is true?

I. The normal distribution is a symmetric, unimodal distribution.
II. T-scores have a mean of 0 and a standard deviation of 1.

1. Only statement I is true.
2. Only statement II is true.
3. Both statements are true.
4. Both statements are false.

Question 2

For a study about the IQ of primary school students, one child scores an exceptional score of 145. The mean IQ is 100, the standard deviation is 15. How many standard deviations does the child's score deviate from the mean?

1. 45
2. 3
3. 1.96
4. 3

Question 3

What is the size of the are under the normal curve from z = 1.5 onward?

1. 0,4394
2. 0,9394
3. 0,0606
4. 0,1200

Question 4

We asked 20 women living in Groningen about their weight. The mean weight of these women is 87 kg with a standard deviation of 5. Between which values will 95% of the women score?

1. 77,2 - 96,8
2. 82,3 - 91,8
3. 72,5 - 101,5
4. 74,5 - 99,5

Question 5

What does an ordinate (one of the axis of a histogram) represent?

1. The different values of X
2. The density of X
3. The frequency of X
4. The chance on X

Open questions with chapter 3

Question 1

You are comparing the sizes of mussels in the sea in two mussel populations using a z-test; the test statistic has the value z = 3.5. What is the most correct conclusion?

Question 2

A professional choice agency uses a standardized IQ test for HAVO students from the highest class. This test has a variance of 225. The scores obtained with this are normally distributed. A sample of 25 students from the group who registered at this agency for advice scores an average of 119 on this test. What is the 95% confidence interval of the population average?

Answers MC-questions with chapter 3

Question 1

A. The normal distribution is symmetric and has only one mode (peak). Statement II does not belong to t-scores, but to z-scores.

Question 2

B. Z = (145-100)/15 = 3

Question 3

C. 2,050X + 0,835

Question 4

A. X = mu +/11,96sigma, so X = 87 +/- 1,96 x 5 = 87 +/- 9,8 = 77,2 until 96,8

Question 5

B. The density of X. This axis is related to the frequency and probability, but is not exactly the same. The possible values of X are shown in the horizontal axis, or abcissa.

Answers Open questions with chapter 3

Question 1

Because a z-test has been used you can assume that the shell sizes are normally distributed and that this is the difference in average shell size between the two populations (the median is used for non-normally distributed quantities). The chance of exceeding s = 3.5 is 0.00023, and this is much smaller than 0.05; there is a significant difference in average shell size between the two populations.

Question 2

113.12 ≤ mu ≤124.88

How can you test hypotheses? - ExamTests 4

MC-questions with chapter 4

Question 1

Which statement is true?

I. With a sampling distribution of the differences between means, we can test the chance that the data occur, assuming that the null hypothesis is true.
II. If the null hypothesis is rejected, this implies that the population means are equal.

1. Only statement I is true.
2. Only statement II is true.
3. Both statements are true.
4. Both statements are false.

Question 2

Which statement is true?

I. A type-I error is the chance to reject H0, while in fact H0 is true.
II. Raising alfa lowers the chance on type-II errors

1. Only statement I is true.
2. Only statement II is true.
3. Both statements are true.
4. Both statements are false.

Question 3

Why are two-sided tests often used in research?

1. Because it is often unclear what the direction of the effect will be.
2. Because researchers want to test as conservatively as possible.
3. Both the above options are correct.
4. Both of the above options are incorrect.

Question 4

Complete the sentence below:

A sampling distribution is the distribution of ... at ... samples.

1. averages; repeated
2. variance; repeated
3. averages; replications of
4. variance; replications of

Open questions with chapter 4

Question 1

Which steps are taken during hypothesis testing?

Question 2

A person is judged and found guilty in a court case. After a few months it appears that this person is innocent and is acquitted. Has a mistake been made here, and if so, which mistake has been made here?

Question 3

The statistical power of a test to demonstrate a certain difference of at least 50% between control group and treated group in an experiment is 0.4. What does this mean?

Question 4

For a research study, the affinity with eating meat was examined for a sample of 134 students. To half of the sample, films were shown before the study about how meat is made. The other half watched a comedy movie. The following data is known: The average of the first group is 4.78 with a standard deviation of 1.61. The average of the second group is 4.54 with a standard deviation of 1.56. Perform the appropriate t-test on this data. Can you reject the null hypothesis when you test one-sided with a = 0.05?

Question 5

A certain matched pairs t-test yields a significant result with a significance level of 5%. The power of this test with a reasonable effect size is 0.12. What is the probability of incorrectly rejecting the null hypothesis?

Question 6

The time that students need to solve an exam question is normally distributed with an average of 30 seconds and a standard deviation of 3 seconds. You want to examine whether the average time mu changes after exercise. You do this by having 9 randomly selected students practice for 30 minutes with the exam question. Then you let them make the specific question and you measure the time, X, that it takes to solve this question. Assume that the standard deviation remains 3 seconds. For which values of x do you reject the null hypothesis that mu equals 30 seconds for a two-sided test with a = 0.01?

Answers MC-questions with chapter 4

Question 1

A. Only statement I is correct. If the null hypothesis is rejected, then the means are not the same.

Question 2

C. Both statements are true.

Question 3

C. Both are correct.

Question 4

A. Averages; repeated. It is a distribution of values (the sample means) for a certain variable, with repeated samples (passing through the same experiment for a large number of samples).

Answers Open questions with chapter 4

Question 1

1. Set up a research hypothesis, for example: People take longer to leave if someone waits for their parking space.
2. Collect samples of both conditions (time with waiting people / no waiting people).
3. Set up up a null hypothesis (H0) that the samples come from populations with the same average: departure times do not depend on whether someone is waiting.
4. Obtain a sampling distribution of differences between averages, assuming H0 is true.
5. Calculate the probability of an average difference at least as large as that we found in the sample.
6. Decide on the basis of that probability whether we can reject or retain H0. If we reject H0, it means that the population means are not the same.

Question 2

A type-I error was made. He was charged while he was not guilty. The null hypothesis is based on our legal system. This states: "You are innocent until your guilt is proven."

Question 3

This means that if there really is a 50% difference, the test gives a significant result in 40% of the cases. The null hypothesis H0 in this test is: there is a difference of less than 50% between control group and treated group; the alternative hypothesis says that there is at least a 50% difference between the two groups. A power of 0.4 means that the probability of rejecting an incorrect H0 is 0.4. To reject H0, a significant result must be found. Because the chance of this is 0.4, this is expected to happen in 40% of the cases.

Question 4

No, p > .05

Question 5

5%

Question 6

For all x values that are less than 27,424 or greater than 32,576

What are the basic concepts of probability? - ExamTests 5

MC-questions with chapter 5

Question 1

There are 100 smarties in a bag: 20% is brown, 19% is yellow, 12% is green, 9% is red and 25% is blue and 15% is orange. What is the chance that I will take a red and a yellow smartie, regardless of the order?

1. 0.034
2. 0.280
3. 0.090
4. 0.191

Question 2

3000 students enroll at Leiden University. 40% of that is male. 800 students enroll in psychology, including 45 men. 1) What is the joint probability that someone is a woman and will study psychology p (V and Psy), and 2)? What is the conditional probability that a man will study something other than psychology p (And | M)?

1. p (V and Psy) = 0.57; p (And | M) = 0.99
2. p (V and Psy) = 0.25; p (And | M) = 0.96
3. p (V and Psy) = 0.57; p (And | M) = 0.96
4. p (V and Psy) = 0.25; p (And | M) = 0.99

Question 3

• Probability that the patient has cancer p (Y +): 15%
• Probability that the patient has no cancer p (Y-): 85%
• Probability of positive diagnosis given that patient has cancer p (X + | Y +): 95%
• Probability of positive diagnosis given that patient has no cancer p (X + | Y-): 5%

Calculate the probability that the patient has given cancer that the patient has received a positive diagnosis p (Y + | X +).

1. 0.52
2. 0.65
3. 0.77
4. 0.90

Question 4

What is the mean and standard deviation of a binomial distribution with n = 12 and p = 0.30?

1. Mean = 6 ; standard deviation = 1.59
2. Mean = 3.6; standard deviation = 1.59
3. Mean = 6; standard deviation = 1.73
4. Mean = 3.6; standard deviation = 1.73

Question 5

Which statement is true?

I. When it comes to probability calculation with discrete variables, we speak of the probability of an outcome within an interval.
II. With combinations, the order of object selection is more important than with permutations.

1. Only statement I is true
2. Only statement II is true
3. Both statements are correct
4. Both statements are false

Answers MC-questions with chapter 5

Question 1

A. p (red, yellow) = 0.09 x 0.19 = 0.0171 and p (yellow, red) = 0.19 x 0.09 = 0.017. The total probability is 0.0171 + 0.0171 = 0.0342.

Question 2

B. Of the 3000 students, 40% are men (= 1200) and 60% are women (= 1800). 800 students enroll in psychology, 45 of them male and 755 female. The probability that someone is a woman and will study psychology is 755/3000 ≈ 0.25. The conditional probability that a man will study something else is (1200-45) / 1200 = 1155/2000 ≈ 0.96

Question 3

C. p (Y+|X+) = (0.95)(0.15)/((0.95)(0.15)+(0.05)(0.85)) = 0.1425/(0.1425 + 0.0425) ≈ 0.77

Question 4

B. Mean = 12 x 0.30 = 3,6. Standard deviation: ≈ 1,59

Question 5

D. Both statements are incorrect. With discrete variables you can speak of the probability of a specific outcome, with continuous variables you can speak of the probability of an outcome within an interval. With permutations, the order is more important in comparison with combinations.

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