HED 241 BIOSTATISTICS IN PUBLIC HEALTH: C 13 PEARSON r

9) Consider a value of r of .65. According to this section, would it always be appropriate to characterize the relationship as being "very strong"?

A value of .65 probably would be characterized as only moderately strong otherwise an exception would be determined by the test given such as GPAs from College Board scores, (64)

7) Is it possible for a relationship to be both direct and weak?

It is possible to be both direct and weak, any positive number above 0 is direct, and when close to 0 is weak such as .15, (Purvis).

8) Is it possible for a relationship to be both inverse and strong?

It is possible to be both inverse and strong where any negative number is inverse and when close to -1.00 is strong such as -.98, (Purvis).

5) Are inverse relationships always weak?

No, inverse relationships closest to -1.00 indicate strong relationship, or even a perfect relationship if r value is -1.00, (63).

4) Which one of the following indicates the strongest relationship? A. .68 B. .77 C. -.98 D. .50

Of the following values: .68, .77, -.98, and .50 the r value of -.98 indicates the strongest relationship, (63).

3) What does a Pearson R of -1.00 indicate?

Pearson r of -1.00 indicates a perfect inverse relationship (63).

2) What does a Pearson r of 0.00 indicate?

Pearson r value of 0.00 indicates the complete absence of a relationship, (63).

perfect relationship

63 -1.00 to 1.00

strong, moderate, weak

63 The farther from 0.00 the stronger the relationship used in conjunction with both positive and negative values of the Pearson r. exact numerical values are not given for these labels because: -interpretation and labeling of an r may vary from one investigator to another and from one type of investigation to another.

absence of a relationship

63 a value of 0.00

The interpretation of a Pearson r varies

63 depending on the type of study.

lower case italicized r

63 symbol for Pearson's statistic often called the Pearson r. full name: Pearson product-moment correlation coefficient.

Karl Pearson developed

63, 1 a very widely used statistic for describing the relationship between two variables. full name: Pearson product-moment correlation coefficient.

properties of the Pearson r

63, 2 1. it can range only form -1.00 to 1.00 2. -1.00 indicates a perfect inverse relationship , which is the strongest possible inverse relationship. 3. 1.00 indicates a perfect direct relationship , which is the strongest possible direct relationship. 4. 0.00 indicates the complete absence of a relationship. 5. the closer a value is to 0.00 , the weaker the relationship. 6. The closer a value is to -1.00 or 1.00, the stronger the relationship.

test reliability

63, 3 is to administer the same test twice to a group of participants without trying to change the participants between administration of test. two scores per examinee, can be correlated through use of the Pearson r.

a professionally constructed test should yield

64 high values of r, such as .75 or higher. endnotes a test is said to be reliable if its results are consistent. ex: if you measured the length of a table twice with a tape measure you would expect very similar results both times- unless your measurement technique was unreliable. .65 probably would be characterized as only moderately strong. endnotes: careful study of the literature on the topic being investigated is needed in order for one to arrive at a non-numerical label or interpretation of a Pearson r that will be accepted by other researchers.

r is not a proportion

64 multiplying it by 100 does not yield percentage.

1) What is the full, formal name of the Pearson r?

The full formal name of the Pearson r is Pearson product-moment correlation coefficient (63).

6) Which one of the following indicates the weakest relationship? A. .93 B. -.88 C. -.95 D. .21

The weakest of the following values .93, -.88, -.95, .21, the value of .21 would be the weakest relationship, (63).

10) Consider a value of r of .50 Would it be appropriate to multiply this value by 100 and to interpret it as representing 50%?

Value r is not a proportion-multiplying it by 100 does not yield a percentage, therefor it would not be appropriate to multiply .50 by 100 and interpret it as representing 50% because .50 is not the half way point between 0.00 and 1.00, (64).