Psy 230 Midterm

For any distribution, what is the z-score corresponding to the mean?

0

What is the value of the median for the following set of scores? Scores: 1, 4, 6, 7, 9, 15, 15, 16, 25, 30

12

Which set of scores below has the smallest standard deviation?

145, 143, 145, 147

What is the value of Σ(X + 2) for the scores 1, 2, 1, and 3?

15

A set of scores ranges from a high of X = 18 to a low of X = 5. If these scores were put in a grouped frequency distribution table with an interval width of 2 points, which of the following would be the top interval in the table?

18-19

In a grouped frequency distribution table, one interval is listed as 35-39. If the scores represent a continuous variable, what are the real limits for this interval?

34.5 and 39.5

For the following distribution of quiz scores, how many individuals had a score of X= 4? X f 6 1 5 6 4 4 3 4 2 2 1 2

4

What is the mode for the population of scores shown in the frequency distribution table? X f 5 3 4 4 3 3 2 3 1 2

4

For the scores shown in the following stem and leaf display, what is the highest score in the distribution? Stem and Leaf Display 4 159 3 098 2 89103 1 39

49

The sum of the squared deviation scores is SS = 50 for a population of N = 10 scores. What is the variance for this population?

5

What is the mean average for the following set of quiz scores? Scores: 4, 5, 9, 2, 3, 7

5

Compute the interquartile range for the following scores that represent a continuous variable: 1, 2, 2, 2, 4, 5, 10, 12

5.5

For a sample with M = 66, a score of X = 55.5 corresponds to z = -1.50. What is the sample standard deviation?

7

For the following data, N = _____. X f 4 2 3 3 2 1 1 2

8

Which of the following statements is correct regarding a biased statistic?

A biased statistic occurs when the average value of a statistic either underestimates or overestimates the corresponding population parameter.

ratio

A comparison of two quantities by division

Sample

A set of individuals selected from a population. Intended to represent the population in a research study.

For the following grouped frequency distribution table, how many people have scores greater than X = 45? X f 60-69 4 50-59 3 40-49 7 30-39 2

Cannot be determined

Why do deviation scores have to be squared before calculating the standard deviation?

If deviation scores are not squared, then the average distance from the mean will always equal 0.

quasi-independent variable

In a nonexperimental study, the "independent variable" that is used to create the different groups of scores is often called the quasi-independent variable.

unusual event

Know that an event is considered to be unusual if the probability of occurring is less than or equal to 0.05 (or 5%).

A sample with M = 85 and s = 12 is transformed into z-scores. After the transformation, what are the values for the mean and standard deviation for the sample of z-scores?

M = 0 and s = 1

After 2 points are subtracted from every score in a sample of size n = 4, the new sample mean is found to be M = 18. What was the mean for the original sample?

M=20

A researcher is interested in average first semester change in weight (gain or loss) for students at a local college. Thus, they record the individual change in weight for a small group of 25 freshman from this college during their first semester. Then, the researcher calculates the average change in weight during the first semester among these 25 students. The average is an example of a ______.

Statistic

interval

The distance between two notes

A sample of n = 5 scores has a mean of M = 7. After one score is removed from the sample, the mean for the remaining scores is found to be M = 6. What was the score that was removed?

X=11

For a population with µ = 65 and σ = 4, what is the X value corresponding to z = -2.25?

X=56

The relationship between a statistic and a sample is the same as the relationship between _____.

a parameter and a population.

Ordinal

consists of a set of categories that are organized in an ordered sequence. Measurements on an ordinal scale rank observations in terms of size or magnitude.

Percentile ranks are closely tied to which of the following terms?

cumulative percentages

Because sample variances are computed by dividing SS by n - 1, the average value of the sample variances from all possible random samples consistently _____ the population variance.

equal

continuous variable

has an infinite number of possible values between any two observed values. Is divided into an infinite number of fractional parts.

A recent study reported that students who just finished playing a prosocial video game were more likely to help others than students who had just finishing playing a neutral or antisocial game. For this study, the kind of game given to the students was the _____.

independent variable

For a perfectly symmetrical distribution, which relationship is always true?

mean=median

If a set of exam scores forms a negatively skewed distribution, what can you likely conclude about the students' scores?

most of the students had relatively high scores

In a frequency distribution graph with negative skew, scores with the highest frequencies are _____ of the distribution.

on the right side

Expirimental

one variable is manipulated while another variable is observed and measured. To establish a cause-and-effect relationship between the two variables, an experiment attempts to control all other variables to prevent them from influencing the results.

Transforming a set of scores into a standardized distribution of z-scores consists of graphically _____ the scores.

relabeling

population

the set of all individuals of interest in a particular study, vary in size; often large.

Correlation

two different variables are observed to determine whether there is a relationship between them.

Under which circumstance below is the median likely to be a better measure of central tendency than the mean?

with an extremely skewed distribution

A sample of n = 5 scores has a mean of M = 10. One new score is added to the sample, and the new mean is calculated to be M = 9. What is the value of the new score?

x=4

For a population with µ = 40 and σ = 8, what is the z-score corresponding to X = 34?

z = -0.75

Which z-score value represents the location farthest from the mean?

z = -2.00

A population has a mean of µ = 15. If 6 points are added to each score, what is the mean for the new distribution of scores?

µ = 21

What is the value of Σ(X - 1)2 for the scores 1, 3, and 4?

13

For a population with µ = 100 and σ = 20, what is the X value corresponding to z = -0.25?

X=95

statistic

a value, usually a numerical value, describes a sample. Derived from measurements of the individuals in the sample.

Parameter

a value, usually a numerical value, that describes a population. Derived from the measurements of the individuals in the population.

discrete variable

has separate, indivisible categories. No values can exist between two neighboring categories.

If a set of scores for a variable is displayed in a frequency distribution polygon, which scale of measurement was used to measure the variable?

interval or ratio

What is the range for the following set of scores obtained for a discrete variable for which 0 is not a possible score? Scores: 5, 7, 9, 13

8

nominal

(adj.) existing in name only, not real; too small to be considered or taken seriously

What is the value of Σ(X + 1) for the scores 2, 3, 5?

13

A set of scores ranges from a low of X = 25 to a high of X = 33 and has a mean of 29. Which of the following is the most likely value for the standard deviation for these scores?

2 points

What is the variance for the following population of scores? Scores: 2, 5, 6, 3

2.50 x-u x-u^2 2. -2. 4 5. 1. 1 6. 2. 4 3. -1. 1 10/4 = 2.50

Last week Tim obtained a score of X = 54 on a math exam with µ = 60 and σ = 8. He also scored X = 49 on an English exam with µ = 55 and σ = 3, and he scored X = 31 on a psychology exam with µ = 37 and σ = 4. For which class should Tim expect the worst grade relative to his peers?

English

A sample of n = 6 scores has a mean of M = 5. One person with a score of X = 19 is added to the distribution. What is the mean for the new set of scores?

M=7

A researcher is measuring the amount of time needed to solve a set of anagrams for a sample of n = 15 students. However, one of the participants fails to solve the problems so the researcher has an undetermined score. What is the best measure of central tendency for these data?

Median

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

Mode

A population with a mean of µ = 9 has ΣX = 54. How many scores are in the population?

N=6

A researcher uses an anonymous survey to investigate the social media habits of American college students. Based on the set of 300 surveys that were completed and returned, the researcher finds that students spend an average of 2 hours each day using social media. The set of 300 students who returned surveys is an example of a _____.

Sample

The average verbal SAT score for the entire class of incoming college freshmen in the United States is 530. However, if a sample of 20 incoming college freshmen is randomly selected from the United States, it is likely that this sample's average verbal SAT score will not be exactly 530. This is consistent with the concept of _____.

Sampling error

Inferential statistics

Study samples to make generalizations about the populations from which they were selected. Interpret experimental data

Descriptive Statistics

Summarize data Organize data Simplify data Familiar example: tables, graphs, averages

Which of the following is a consequence of increasing variability?

The distance from one score to another tends to increase and a single score tends to provide a less accurate representation of the entire distribution.

Which of the following statements is consistent with a research study conducted with the correlational method?

Two variables are measured, and there is only one group of participants.

A sample of n = 20 scores has a mean of M = 32 and a standard deviation of s = 6. In this sample, what is the z-score corresponding to X = 28?

z=-0.67

A population has µ = 30 and σ = 10. If 5 points are added to every score in the population, what are the new values for the mean and standard deviation?

µ = 35 and σ = 10

Mark is provided a score of X = 57 that corresponds with a z-score of z = 1.60 to describe his performance on a graduate entrance exam. The graduate entrance exam has a standard deviation of σ = 10. What is the mean average for this graduate entrance exam?

µ = 41

A population of N = 6 scores has ΣX = 42. What is the population mean?

µ = 7

A person scores X = 65 on an exam. Which set of parameters would give this person the worst grade on the exam relative to others?

µ = 70 and σ = 5

In a population of scores, X = 83 corresponds to z = -0.50 and X = 93 corresponds to z = +2.00. What are the values for the population mean and standard deviation?

µ = 85 and σ = 4

Which of the following symbols identifies the population standard deviation?

σ