Psychology2016

A-10 APPENDIX A

Practice Quiz How much do you remember?

Pick the best answer.

1. Dr. Kopelowoski has just given an examination to his Introduction
   to Psychology class. Because this is a class of more than
   500  students, it would be difficult for him to assess the results
   looking at each score one at a time. If he wants to know how
   many students earned an A, a B, and so on, which of the
   following might be the best for him to program his computer
   to provide?
   a. A measure of central tendency
   b. A mean
   c. A frequency distribution
   d. A correlation coefficient


2. Because of its very specific shape, a “normal” distribution is also
   often described as a ____ curve.
   a. bell
   b. positively skewed
   c. negatively skewed
   d. multimodal
   3. Aaron has just received his grade on the third exam of his chemistry
   class. He earned a 90 on this test. He is happy because his grades
   have been steadily increasing since the start of the term. On the
   first exam he earned an 80, and on the second exam he earned an
   85. Which of the following represents the approximate mean of the
   three exam scores?
   a. 80
   b. 85
   c. 88
   d. 255
   4. Which of the following would be most useful if you want to know
   how many standard deviations from the mean a single score in a
   data set falls?
   a. A t-score
   b. A z score
   c. A deviation coefficient
   d. A variance determination

Inferential Statistics

Descriptive methods of statistics are useful for organizing and summarizing numbers or

scores. But what method is useful when it comes to comparing sets of numbers or scores

to see if there are differences between them that are great enough to be caused by some-

thing other than chance variation?

LOOKING AT DIFFERENCES: STATISTICAL SIGNIFICANCE

A.5 Describe how inferential statistics can be used to determine if differences in

sets of data are large enough to be due to something other than chance variation.

Inferential statistics consist of statistical techniques that allow researchers to determine

the difference between results of a study that are meaningful and those that are merely

due to chance variations. Inferential statistics also allow researchers to draw conclusions,

or make inferences, about the results of research and about whether those results are only

true for the specific group of animals or people involved in the study or whether the

results can be applied to, or generalized to, the larger population from which the study

participants were selected.

For example, in the Cheryan (Cheryan et al., 2009) study of the difference in male

and female students’ attitudes toward computer science when exposed to environments

that were either stereotypically masculine or nonstereotypical, there were a lot of vari-

ables that simply could not be controlled completely, even with random assignment of

participants to the two conditions. to Learning Objective 1.1. For example, there

was no guarantee that random assignment would account for the interfering effects of

female participants who might have really liked the science fiction toys, posters, and

pizza they saw in one of the test conditions. Maybe any difference found between the

males and females was due to pure luck or chance and not to the variables under study.

In any analysis that compares two or more sets of data, there’s always the possi-

bility of error in the data that comes either from within the group (all participants in one

group, for example, will not be exactly like each other) or differences between groups

(the experimental group and the control group are formed with different people, so there

inferential statistics

statistical analysis of two or more

sets of numerical data to reduce the

possibility of error in measurement

and to determine if the differences

between the data sets are greater than

chance variation would predict.

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