Stat Exam 1

Front 1

Descriptive Statistics are used for what?

Back 1

to simplify and summarize data

Front 2

Inferential Statistics are used for what?

Back 2

to make general conclusions about populations

using sample data.

Front 3

How could a difference be caused by the treatments?

Back 3

Treatments 1 & 2 affect individuals differently, so the scores of the individuals receiving treatment 1 are different from those of individuals receiving treatment 2.

Front 4

How could a difference simply be sampling error?

Back 4

The two treatments do not have different effects, but the individuals in one sampledo not behave exactly like the individuals in the second sample.

Front 5

What additional information is obtained from measurements on an ordinal scale compared to measurements on a nominal scale?

Back 5

The direction of the difference between 2 measurements

Front 6

What additional information is obtained from measurements on an interval scale compared to measurements on an ordinal sclae?

Back 6

The magnitude of the difference between 2 measurements

Front 7

What additional information is obtained from measurements on a ratio scale compared to measurements on an interval scale?

Back 7

the relative sizes of two measurements

Front 8

A numerical value that describes a sample data set is called a

Back 8

statistic

Front 9

A numerical value that describes a population data set is called a

Back 9

parameter

Front 10

Why is it necessary to have more than one method for measuring central tendency?

Back 10

Because no single method works well in all situations.

Front 11

Why is the mean often not a good measure of central tendency for a skewed distribution?

Back 11

Extreme scores can displace the mean toward the tail

Front 12

For a negatively skewed distribution with a mean of M=20, what is the most probable value for the median?

Back 12

greater than 20

Front 13

For a perfectly symmetrical distribution with a median of 30, what is the value of the mean?

Back 13

30

Front 14

Describe the data for a correlational research study.

Back 14

A correlational study has only one group of individuals and measures two (or more) different variables for each individual.

Front 15

experimental?

Back 15

manipulating 2 variables

Front 16

nonexperimental?

Back 16

observation

Front 17

f?

Back 17

frequency of X

Front 18

What general purpose is served by a good measure of central tendency?

Back 18

The purpose of central tendency is to identify a single score that serves as the best representative for an entire distribution, usually a score from the center of the distribution.

Front 19

Identify the circumstances in which the median rather than the mean is the preferred measure of central tendency.

Back 19

The median is used instead of the mean when there is a skewed distribution (a few extreme scores), an open-ended distribution, undetermined scores, or an ordinal scale.

Front 20

SS

Back 20

SS is the sum of squared deviation scores.

Front 21

Variance

Back 21

Variance is the mean squared deviation.

Front 22

Standard deviation

Back 22

Standard deviation is the square root of the variance. It provides a measure of the standard distance from the mean.

Front 23

Is it possible to obtain a negative value for the variance or the standard deviation?

Back 23

Standard deviation and variance are measures of distance and are always greater than or equal to zero.

Front 24

Explain why the formulas for sample variance and population variance are different.

Back 24

Without some correction, the sample variance underestimates the variance for the population. Changing the formula for sample variance (using n − 1 instead of N) is the necessary correction.

Front 25

After 3 points have been added to every score in a sample, the mean is found to be M = 83 and the standard deviation is s = 8. What were the values for the mean and standard deviation for the original sample?

Back 25

The original mean is M = 80 and the standard deviation is s = 8.

Front 26

After every score in a sample has been multiplied by 4, the mean is found to be M = 48 and the standard deviation is s = 12. What were the values for the mean and standard deviation for the original sample?

Back 26

The original mean is M = 12 and the standard deviation is s = 3.

Front 27

What information is provided by the sign (+/−) of a z-score? What information is provided by the numerical value of the z-score?

Back 27

The sign of the z-score tells whether the location is above (+) or below (−) the mean, and the magnitude tells the distance from the mean in terms of the number of standard deviations.

Front 28

What are the two requirements that must be satisfied for a random sample?

Back 28

The two requirements for a random sample are: (1) each individual has an equal chance of being selected, and (2) if more than one individual is selected, the probabilities must stay constant for all selections.

Front 29

What information is provided by the sign (+ or −) of the Pearson correlation?

Back 29

A positive correlation indicates that X and Y change in the same direction: As X increases, Y also increases. A negative correlation indicates that X and Y tend to change in opposite directions: As X increases, Y also decreases.