# PSY-3301 Exam#2

Question 1

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If one takes a sample of pairs of points over a narrow range of X or Y scores, what effect might this have on the value of r?

Question 2

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What is the slope for the points X1 = 30, Y1 = 50 and X2 = 25 and Y2 = 40?

Question 3

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A z distribution always is normally shaped.

Question 4

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In a linear relationship all the points must fall on a straight line.

Question 5

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It is possible to compute a coefficient of correlation if one is given _________.

Question 6

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A researcher wanted to know if the order in which runners finish a race is correlated with their weight. She conducts an experiment and the data are given below.

Finishing order

1

2

3

4

5

6

Weight (lbs)

110

114

112

108

116

113

What is the appropriate correlation coefficient for these data?

Question 7

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A raw score that is 1 standard deviation above the mean of the raw score distribution will have a z score of 1.

Question 8

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The standard deviation of the z distribution equals _________.

Selected Answer:

b.

1

Correct Answer:

c.

0 and the variance of the z distribution

Question 9

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A z score is a transformed score.

Question 10

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By changing the value of one score in a sample this will necessarily cause the mode to change.

Question 11

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If one calculates r for a set of numbers and then adds a constant to each value of one of the variables, the correlation will change.

Question 12

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A correlation coefficient expresses quantitatively the degree of relationship between two variables.

Question 13

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The standard deviation of the z distribution equals _________.

Question 14

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The mean of the z distribution equals _________.

Question 15

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The closer the points on a scatter diagram fall to the regression line, the _________ between the scores.

Question 16

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The range of a correlation coefficient is 0 to +1.

Question 17

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The use of z scores allows comparisons between variables measured on different scales and units.

Question 18

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In a bell-shaped distribution, _________.

Question 19

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A testing bureau reports that the mean for the population of Graduate Record Exam (GRE) scores is 500 with a standard deviation of 90. The scores are normally distributed.

The percentile rank of a score of 667 is _________.

Question 20

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In a negatively skewed distribution, the mean will generally be _______ the median.

Question 21

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All standard scores are z scores.

Question 22

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A distribution has a mean of 60.0 and a standard deviation of 4.3. The raw score corresponding to a z score of -1.51 is _________.

Question 23

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A distribution has a mean of 60.0 and a standard deviation of 4.3. The raw score corresponding to a z score of 0.00 is _________.

Question 24

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A correlation coefficient expresses the direction but not the magnitude of a relationship.

Question 25

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The normal curve is a symmetric, bell-shaped curve.

Question 26

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When calculating the population standard deviation, we use N – 1 in the denominator.

Question 27

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The correlation coefficient when N = 2 is meaningless.

Question 28

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If a group of 100 people has an average IQ of 107 and a group of 50 people has an average IQ of 101, the average IQ of all the people is 105.

Question 29

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A stockbroker has kept a daily record of the value of a particular stock over the years and finds that prices of the stock form a normal distribution with a mean of $8.52 with a standard deviation of $2.38.

The percentage of scores that lie between $9.00 and $10.00 is _________.

Question 30

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In a plot of the normal curve, frequency is plotted on the X axis.

Question 31

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It is possible to have a set of scores with three different values for central tendency.

Question 32

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A deviation score is the same thing as a raw score.

Question 33

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A testing bureau reports that the mean for the population of Graduate Record Exam (GRE) scores is 500 with a standard deviation of 90. The scores are normally distributed.

The proportion of scores that lie above 650 is _________.

Question 34

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Causation implies correlation.

Question 35

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Which of the following is (are) not correlation coefficients?

Question 36

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We use N – 1 in the denominator of the equation for calculating the sample standard deviation because it provides us with an accurate estimate of the population standard deviation.

Question 37

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Which of the following statements is true?

Question 38

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The mean is the most sensitive measure of central tendency to extreme scores.

Question 39

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Which Pearson correlation coefficient shows the strongest relationship between two variables?

Question 40

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An industrial psychologist observed 8 drill-press operators for one working day. She recorded the number of times each operator pressed the “faster” button instead of the “stop” button to determine whether the design of the control panel was contributing to the high rate of accidents in the plant. The resulting scores were as follows:

5, 2, 8, 2, 3, 2, 4, 12

The standard deviation for this distribution is _________. Assume sample data.

Question 41

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Central tendency and variability are synonymous.

Question 42

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The correlation coefficient r is a descriptive statistic.

Question 43

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If the value of r on ratio scaled raw data were 0.87 and the pairs of numbers were converted to ordinal data, and r calculated for the ordinal data, r would equal 0.87.

Question 44

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An industrial psychologist observed 8 drill-press operators for one working day. She recorded the number of times each operator pressed the “faster” button instead of the “stop” button to determine whether the design of the control panel was contributing to the high rate of accidents in the plant. The resulting scores were as follows:

5, 2, 8, 2, 3, 2, 4, 12

The variance for this distribution is _________. Assume sample data.

Question 45

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Assume one has a set of 35 scores with = 100 and s = 9. If 5 scores, each equal to 100 were added to the distribution, what effect would this have on ?

Question 46

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A testing service has 1000 raw scores. It wants to transform the distribution so that the mean = 10 and the standard deviation = 1. To do so, _________.

Question 47

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Given the following set of scores

X: 10, 12, 6, 8, 9, 11, 13, 13, 5, 0, 1

What is the median?

Question 48

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r decreases as N decreases.

Question 49

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The standard deviation of the z distribution is always equal to 1.0.

Question 50

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If a correlation is perfect,