PSY 230 Midterm #1 Questions

Define the concept of "sampling error." Note: your definition should include the concepts of sample, population, statistic, and parameter.

A sampling error is an error within a data set that is not purposeful, it happens when a sample does not match and represent an entire population. When a sample is taken from a statistic, sometimes it will not match up with a parameter of a population due to the different people and opinions in each group on the subject of the data. A sampling error will occur when the sample of the data is different from the population. Its random and it happens because one group (sampling group) may not represent and entire population.

Without some correction, sample variability is said to be "biased." Define the term biased, and explain how this bias is corrected in the formula for sample variance.

Biase means it is overestimated or underestimated. The bias is corrected by degree of freedom n-1. Sample mean is unbiased and finds the average. The bias is corrected by degree of freedom n-1 instead of degrees of freedom of n. Sample mean is unbaised as its expectation value is equal to population mean.

A group of quiz scores ranges from 3 to 10, but no student had a score of X = 5. If the scores are put in a frequency distribution table, X = 5 would not be listed in the X column. True False

False

A recent study found a correlation between gum disease and heart disease. This result indicates that gum disease causes people to develop heart disease. True False

False

A sample of n = 8 scores has a mean of M = 16. For this sample, ΣX = 2. True False

False

It is possible to have a distribution of scores where no individual has a score exactly equal to the mode. True False

False

A correlational study typically uses only one group of participants but measures two different variables (two scores) for each individual. True False

True

A researcher is interested in the average income for registered voters in the United States. The entire group of registered voters is an example of a population. True False

True

For the following scores, ΣX2 = 35. Scores: 1, 3, 5 True False

True

If a sample has an odd number of scores, at least one individual will have a score exactly equal to the median. True False

True

It is possible for a distribution to have more than one mode. True False

True

To calculate the variance for a sample, SS is divided by df = n - 1. True False

True

What is the mode for the following sample of n = 8 scores? Scores: 0, 1, 1, 1, 2, 2, 3, 3 a) 1 b) 1.5 c) 13/8 = 1.625 d) 3

a) 1

What is the mode for the population of scores shown in the frequency distribution table? X f 5 1 4 2 3 3 2 4 1 2 a) 2 b) 3 c) 3.5 d) 4

a) 2

A population of N = 5 scores has ΣX = 20 and ΣX^2 = 100. For this population, what is the value of SS? a) 20 b) 380 c) 100 d) 80

a) 20

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 _____. a) 50 b) greater than 50 c) less than 50 d) impossible to determine without additional information

a) 50

Which of the following actions will always change the value of the mean? a) Changing the value of one score b) Adding a new score to the distribution c) Removing a score from the distribution d) All 3 of the other choices are correct

a) Changing the value of one score

If a set of exam scores forms a negatively skewed distribution, what can you conclude about the students' scores? a) Most of the students had relatively high scores. b) Most of the students had relatively low scores. c) About 50% of the students had high scores and the rest had low scores. d) It is not possible to draw any conclusions about students' scores.

a) Most of the students had relatively high scores.

In a frequency distribution graph, frequencies are presented on the , and the scores (categories) are listed on the . a) Y axis; X axis b) X axis; Y axis c) horizontal line; vertical line d) class interval; horizontal line

a) Y axis; X axis

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 _______. a) statistic b) constant c) variable d) parameter

a) statistic

A sample of n = 15 scores ranges from a high of X = 11 to a low of X = 3. If these scores are placed in a frequency distribution table, how many X values will be listed in the first column? a) 8 b) 9 c) 10 d) It depends on whether any scores have a zero frequency.

b) 9

One sample with n = 4 scores has a mean of M = 12, and a second sample with n = 6 scores has a mean of M = 8. If the two samples are combined, what is the mean for the combined set of scores? a) 4.8 b) 9.6 c) 10.0 d) 19.2

b) 9.6

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? a) Statistical error b) Sampling error c) Parametric error d) Inferential error

b) Sampling error

Which of the following is an example of a continuous variable? a) The number of children in a family b) The amount of time to solve a problem c) The number of males in each class offered by the college d) The gender of each student in a psychology class

b) The amount of time to solve a problem

A recent study reports that students who just finished playing a prosocial video game were more likely to help others than students who had played a neutral or antisocial game. For this study, what is the independent variable? a) The students who were given the neutral or antisocial game b) The kind of game given to the students c) The students who were given the prosocial game d) The helping behavior of the student

b) The kind of game given to the students

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? a) The mean b) The median c) The mode d) Central tendency cannot be determined for these data

b) The median

A distribution of scores has a mean of μ = 50. One new score is added to the distribution, and the new mean is found to be μ = 48. From this result, you can conclude that the new score was _____. a) greater than 50 b) less than 50 c) equal to 48 d) cannot answer from the information given

b) less than 50

In a distribution with positive skew, scores with the highest frequencies are _____. a) represented at two distinct peaks b) on the left side of the distribution c) on the right side of the distribution d) in the middle of the distribution

b) on the left side of the distribution

Which of the following symbols identifies the sample variance? a) s b) s^2 c) σ d) σ ^2

b) s^2

What is the range for the following set of scores? Scores: 5, 7, 9, 15 a) 4 points b) 5 points c) 10 or 11 points d) 15 points

c) 10 or 11 points

A set of scores ranges from a high of X = 24 to a low of X = 5. If these scores were put in a frequency distribution table with an interval width of 2 points, which of the following would be the top interval in the table? a) 4-5 b) 23-24 c) 24-25 d) 22-24

c) 24-25

What is the mean for the following sample of scores? Scores: 1, 4, 5, 6 a) 4.5 b) 16 c) 4 d) 8

c) 4

Which of the following statements cannot be true for a distribution of scores? a) No one has a score exactly equal to the mean. b) No one has a score exactly equal to the median. c) No one has a score exactly equal to the mode. d) All of the other options are false statements.

c) No one has a score exactly equal to the 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 a) n = 5 b) n = 15 c) n = 21 d) Cannot be determined

c) n = 21

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 _________. a) parameter; population b) population; sample c) sample; population d) statistic; sample

c) sample; population

Which set of scores has the smallest standard deviation? a) 27, 105, 10, 80 b) 5, 11, 42, 22 c) 11, 17, 31, 53 d) 145, 143, 145, 147

d) 145, 143, 145, 147

A sample of n = 25 scores has M = 20 and s^2 = 9. What is the sample standard deviation? a) 81 b) 4.5 c) 9 d) 3

d) 3

The sum of the squared deviation scores is SS = 20 for a population of N = 5 scores. What is the variance for this population? a) 5 b) 100 c) 80 d) 4

d) 4

What is the value of (ΣX)2 for the scores 1, 0, 2, 4? a) 21 b) 14 c) 28 d) 49

d) 49

What is the value of SS for the following set of scores? Scores: 1, 1, 4, 0 a) 10 b) 18 c) 6 d) 9

d) 9

A researcher surveys a sample of n = 200 college students and asks each person to identify his or her favorite movie from the past year. If the results were presented in a frequency distribution graph, what kind of graph would be appropriate? a) A histogram b) A polygon c) A histogram or a polygon d) A bar graph

d) 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. a) nominal b) ratio c) interval d) ordinal

d) ordinal