Question 1

A bell-shaped distribution,with a large number of scores in the middle,tapering to very few extremely high and low scores is known as a negatively-skewed curve.

Accepted Answer

The given description actually corresponds to a normal distribution, which is symmetrical and not skewed. A negatively-skewed curve would have more scores towards the higher end and taper off towards lower scores.

Question 2

For the numbers 10,16,3,7,and 17,the range is 14.

Accepted Answer

To find the range of a set of numbers, you subtract the smallest number from the largest number.

In this case, the smallest number is 3 and the largest number is 17.

Range = 17 - 3 = 14

Therefore, the statement is true.

Question 3

After administering a unit test to her psychology students,a college professor calculates the mean and range for this test in order to better understand the performance of her students on the material in this unit.This professor is using inferential statistics.

Accepted Answer

The professor is actually using descriptive statistics to summarize and analyze the performance of her students on the test. Inferential statistics would involve making conclusions or predictions about a larger population based on the data from a sample.

Question 4

Ninety-five percent of all cases are found between a standard deviation of +2 and a standard deviation of -2 on a normal curve.

Accepted Answer

This statement is true as it represents the empirical rule in statistics, where about 95% of the data falls within two standard deviations of the mean on a normal distribution.

Question 5

Vertical bars are used to indicate frequencies in a frequency polygon.

Accepted Answer

Vertical bars are used in a histogram to represent frequencies, while a frequency polygon uses line segments to connect points representing the frequencies at each interval.

Question 6

A frequency distribution is made by breaking down the entire range of possible scores into classes of equal size and then recording the number of scores falling into each class.

Accepted Answer

This is a correct definition of a frequency distribution.

Question 7

If your psychology test scores include 100,100,100,80,and 70,then the mean is 90.

Accepted Answer

To find the mean, we add up all of the scores and then divide by the total number of scores. In this case, (100+100+100+80+70)/5 = 90. Therefore, the mean is indeed 90.

Question 8

The three basic types of descriptive statistics are graphical statistics,measures of central tendency,and measures of variability.

Accepted Answer

Graphical statistics, measures of central tendency, and measures of variability are indeed the three basic types of descriptive statistics.

Question 9

Direct measurement has shown such characteristics as height,memory span,and intelligence to be distributed approximately along a normal curve.

Accepted Answer

Direct measurement has shown that many characteristics follow a normal distribution, which means that the majority of individuals fall around the average (mean) value of the trait, and fewer individuals fall on either extreme end of the distribution. This is commonly referred to as the "bell curve." Height, memory span, and intelligence are some examples of traits that have been found to follow a normal distribution in the population.

Question 10

The median is very sensitive to extremely high or low scores.

Accepted Answer

The median is a measure of central tendency that is not sensitive to extreme values, as it is the middle value of a data set when ordered from least to greatest.

Question 11

The simplest way of visualizing a correlation is to construct a scatter diagram.

Accepted Answer

A scatter diagram is a graph that plots the values of two variables as points on a coordinate plane. It is a simple and effective way to visualize the correlation between two variables.

Question 12

Ten music majors take a 20-point quiz on the musical scales.Their scores were as follows:
12,13,15,15,16,16,17,18,19,20.The median of these scores is 16.

Accepted Answer

The scores are already arranged in ascending order as 12, 13, 15, 15, 16, 16, 17, 18, 19, 20. The middle score is 16, which means it is the median score. Therefore, the statement is true.

Question 13

If two students take psychology midterms,but in different classes,it is impossible to tell whether each student scored at the top,middle,or bottom of their classes unless you know what the average score was on each test.

Accepted Answer

Without knowing the average scores on each test, we cannot determine the relative position of each student's score within their respective classes.

Question 14

The relationship of the standard deviation to the normal curve makes it possible to compare groups of scores if they come from distributions that are approximately normal.

Accepted Answer

The standard deviation is a measure of the spread of scores in a distribution, and when the distribution is approximately normal, it follows a specific pattern that can be represented by the normal curve. Therefore, when comparing groups of scores that come from distributions that are approximately normal, the standard deviation can be used to assess how much variation there is within each group and to compare the groups based on their relative dispersion.

Question 15

The index of how much a typical score differs from the mean of a group of scores is known as the Pearson r.

Accepted Answer

The statement is incorrect. The index of how much a typical score differs from the mean of a group of scores is known as the standard deviation, not the Pearson r. The Pearson r is a measure of the strength and direction of the linear relationship between two variables.

Question 16

A correlational study would be used to determine if a relationship existed between rainfall levels and crime rates.

Accepted Answer

A correlational study is used to determine whether a relationship exists between two variables. In this case, the two variables are rainfall levels and crime rates, and the study would aim to determine whether there is a correlation, or a tendency for them to vary together.

Question 17

Given these scores 40,40,30,50,30,20,40,20,50,40,the mode is 30.

Accepted Answer

The mode is the number that appears most frequently in a data set. In this case, 40 appears most frequently, not 30.

Question 18

If the mean on a test is 90 and the standard deviation is 10,a person with a z-score of -1.0 scored 110 on the test.

Accepted Answer

A z-score of -1.0 indicates that the person scored 1 standard deviation below the mean. Therefore, their actual score would be:

Score = (z-score x standard deviation) + mean
Score = (-1.0 x 10) + 90
Score = 80

Since the person's actual score is 80 and not 110, the statement is false.

Question 19

The fewer absences that students have,the higher their grade point average.This illustrates a negative relationship.

Accepted Answer

A negative relationship means that as one variable increases, the other variable decreases. In this case, as the number of absences decreases, the grade point average increases.

Question 20

Measures of variability provide a single score that describes how scattered or "spread out" a distribution of scores is.

Accepted Answer

Measures of variability, such as range, variance, and standard deviation, are used to quantify the extent to which scores in a distribution vary from each other. They provide a single numerical value that summarizes the degree of dispersion in the data set.

Quiz 20: Appendix B: Behavioral Statistics