psy 230 statistics of behavioral sciences exam 1

Which set of scores has the smallest standard deviation?

145, 143, 145, 147

A population of N = 5 scores has ∑x=20 and ∑x^2=100. for this population, what is the value of SS?

20

A population has SS = 100 and σ^2=4. how many scores are in the population?

25

For a perfectly symmetrical distribution with µ = 30, what is the most probable value for the mode?

30

A population of N = 5 scores has ∑x=20 and ∑x^2=120. for this population, what is the value of SS?

40

The sum of the squared deviation scores is SS = 20 for a sample of n = 5 scores. What is the variance for this sample?

5

A sample of n = 8 scores has SS = 50. If these same scores were a population, then the SS value for the population would be ____.

50

What is the value of the median for the following set of scores? Scores: 1, 3, 4, 6, 7, 8, 12, 23

6.5

Classroom 1 with n = 10 scores has an exam mean of M = 96.5. Classroom 2 with n = 20 scores has an exam mean of M = 85. What is the combined weighted mean?

88.83

X f cf c% 25-29 2 20 100% 20-24 5 18 90% 15-19 5 13 65% 10-14 6 8 40% 5-9 2 2 10% _ Refer to Table 2.6. What is the percentile rank corresponding to a score of X = 24.5?

90%

What is the first step to be performed in the following mathematical expression? (∑x)2

Add the scores.

Around 70% of the scores will be located within one standard deviation of the mean.

Around 70% of the scores will be located within one standard deviation of the mean.

Which of the following is an example of a discrete variable?

The biological sex of each student in a psychology class

A recent study reports that elementary school students who were given a nutritious breakfast each morning had higher test scores than students who did not receive the breakfast. For this study, what is the independent variable?

Whether or not a breakfast was given to the students

If the following distribution was shown in a histogram, the bar above the 15-19 interval would reach from ____ to ____. X f 20-25 2 15-19 5 10-14 4 5-9 1

X = 14.5 to X = 19.5

X f cf c% 25-29 2 20 100% 20-24 5 18 90% 15-19 5 13 65% 10-14 6 8 40% 5-9 2 2 10% Refer to Table 2.6. Sixty-five percent of the scores are at or below a score of ____.

X= 19.5

For the distribution in the following table, what is the 50th percentile? X c% 9 100% 8 80% 7 50% 6 25%

X= 7.5

In a frequency distribution graph, frequencies are presented on the ____ and the scores (categories) are listed on the ____.

Y axis/X axis

For a set of scores separated into "Male" and "Female" categories, the mean and median are appropriate measures of central tendency.

false

In a relaxation training experiment, researchers randomly assign participants to receive either 0, 2, 4, or 8 training sessions and then measure time it takes them to fall asleep. This means there are four independent variables in this experiment

false

A researcher measures eye color for a sample of n = 50 people. Which measure of central tendency would be appropriate to summarize the measurements?

mode

For the following frequency distribution of quiz scores, how many individuals took the quiz? X f 5 6 4 5 3 5 2 3 1 2

n= 21

The students in a psychology class seemed to think that the midterm exam was very easy. If they are correct, what is the most likely shape for the distribution of exam scores?

negatively skewed

What frequency distribution graph is appropriate for scores measured on a nominal scale?

only a bar graph

Determining the class standing (1st, 2nd, and so on) for the graduating seniors at a high school would involve measurement on a(n) ____ scale of measurement.

ordinal

What is the shape for the distribution shown in Figure 2.2?

positively skewed

Which of the following symbols identifies the sample variance?

s^2

A set of 10 scores has SS = 90. If the scores are a sample, the sample variance is ____ and if the scores are a population, the population variance is ____.

s^2=10;σ^2=9

Although a research study is typically conducted with a relatively small group of participants known as a __, most researchers hope to generalize their results to a much larger group known as a_____.

sample; population

The average verbal SAT score for the entire class of entering freshmen is 530. However, if you select a sample of 20 freshmen and compute their average verbal SAT score you probably will not get exactly 530. What statistical concept is used to explain the natural difference that exists between a sample mean and the corresponding population mean?

sampling error

A researcher records the change in weight (gain or lost) during the first semester of college for each individual in a group of 25 freshmen, and calculates the average change in weight. The average is an example of a ____.

statistic

For an experiment comparing two methods for teaching social skill training to autistic children, the independent variable is ____ and the dependent variable is ____.

teaching methods; the social skills that are learned

A sample of n = 6 scores has ∑X = 48. This sample has a mean of M = 8

true

For a distribution with one or two extreme scores, the median is usually a more representative value than the mean.

true

For a set of scores measured on an ordinal scale, the median is the preferred measure of central tendency.

true

If a researcher measures two individuals on an ordinal scale, then it is impossible to determine how much difference exists between the two people.

true

In a sample of n = 3 scores, two scores are each below the mean by 2 points. The third score must then be above the mean by 4 points.

true

Which of the following symbols identifies the population standard deviation?

σ

On an exam with a mean of μ = 70, you have a score of X = 75. Which of the following values for the standard deviation would give you the highest position within the class?

σ= 1

On an exam with a mean of μ = 70, you have a score of X = 65. Which of the following values for the standard deviation would give you the highest position within the class?

σ=10