Psych 10 HW 2

The mean is an appropriate measure of central tendency for

-all of these -data that are unimodal and symmetrically -distributed data that are on an interval or ratio scale -data in which the mean, median, and mode are equal Answer: all of these

The median is an appropriate measure of central tendency for

-data that are positively skewed -all of these -data that are on an ordinal scale -data that are negatively skewed Answer: all of these

A researcher records the time in seconds it takes a sample of participants to walk alone through a dark portion of campus. The researcher computes SS = 1,200. Assuming that a sample of 25 participants was observed in this study, what is the standard deviation for these data?

7.1 s

A researcher records the following scores on a working memory quiz for two samples. Which sample has a larger standard deviation? Sample A: 2, 3, 4, 5, 6, 7, and 8 Sample B: 4, 5, 6, 7, 8, 9, and 10

Both samples have the same standard deviation

A researcher records the following data for the time (in seconds) it takes five rats to cross an electrical grid to obtain reinforcement on the other side: 12, 9, 13, 4, and 12. Is the mean equal to the mode in this example?

No; the mode is larger than the mean

A researcher measures the number of trials it takes two samples of participants to master a new task. In both samples, SS = 240. Sample A consisted of 12 participants and Sample B consisted of 18 participants. Which sample is associated with a larger variance?

Sample A

Which of the following is the best explanation for why the standard deviation is almost always reported with the mean?

The standard deviation measures the spread of scores from the mean, so it is important to know both the mean and the standard deviation.

A professor grades 120 research papers and reports that the average score was an 80%. What do we know about the sum of the differences of these 120 scores from their mean of 80%?

The sum of the differences is equal to zero.

When would it be appropriate to calculate a population mean?

When data are measured for all members of a population

A researcher records the following data for the number of dreams recalled during a night of sleep for 10 college students: 3, 2, 4, 4, 3, 1, 1, 0, 2, and 0. Is the mean equal to the median in this example?

Yes

What terms refer to the meaning of each of the following measures, respectively: mean, median, and mode

average, middle, and most

The mathematical term ∑X is the numerator for

both population mean and sample mean

The distribution of annual household income in the United States is positively skewed. If the median annual income is about $56,000, this implies that the mean annual household income in the United States is

larger

The ______ is the sum of all scores (in a sample or population) divided by the number of scores summed

mean

The variance and standard deviation can never be ______.

negative

If a portion of people from a population are asked to complete an assessment, then the average score among that group of people would be considered a

sample mean

A researcher records 52 scores. What is the median position of these scores?

the average of the 26th and 27th scores in numeric order

The mode can be used with the mean to describe which of the following variables?

the winning percentage of teams in a league

Regardless of the number of scores in a distribution, the range only includes ______ score(s) in its calculation.

two

Each deviation in the numerator for variance is squared because ______.

without squaring each deviation, the solution for SS would be zero