Psychology.okstate.edu



Name: ______________________________ Psyc 3214 / Fall, 2016 / Pearson’s r

1. A researcher wants to investigate the well-established relationship between lead intake and developmental problems in a sample of Peruvian children. The researcher tests the levels of lead in the blood of 11 six-year-old children. She also assesses the children’s motor skills and physical development using a well-known test. The lead is measured in micrograms per deciliter that has been shown to range between 0 and 120 (high scores indicate more lead), and the motor skills test ranges in value from 0 to 50 (high scores indicate higher functioning). The data follow:

Lead Skills

45 25

25 35

40 30

21 50

78 15

62 10

65 22

42 40

21 17

33 32

17 41

Do you expect the sign of the correlation to be positive or negative? (Pos, Neg)

Do the data reveal a linear relationship between lead and motor functioning? Use the space above and below to conduct an NHST. Use an alpha of .05, and show all of your work.

1. Pearson’s correlation coefficient can detect both linear and curvilinear (that is, nonlinear) relationships between two variables. ( True / False )

2. Which of the scatterplots below demonstrates the largest, positive correlation?

[pic]

3. A correlation of -1.0 __________.

a. indicates a slight, negative relationship

b. means that the two variables are not related

c. suggests that the relationship between the two variables is nonlinear

d. indicates a perfect positive relationship since the sign of the correlation is arbitrary

e. both a and c

f. none of the above

4. Which of the following is TRUE?

a. Generally speaking, as the correlation coefficient gets larger than 1, the more evidence there is for an association between two variables.

b. A negative chi-square value indicates a negative relationship between two variables.

c. The covariance can range, in theory, from negative infinity to positive infinity.

d. All of the above are false

5. The sampling distribution of Pearson’s r is ___________ when the null hypothesis is true.

a. mesokurtic b. skewed right

c. leptokurtic d. skewed left

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