Exam 1, 311

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 = 1,000. Assuming that a sample of 11 participants was observed in this study, what is the standard deviation for these data?

10 seconds

A researcher decides to split scores on an exam into quartiles. She determines that a score of 64 is at the 25th percentile, a score of 74 is at the 50th percentile, and a score of 80 is at the 75th percentile. What is the interquartile range (IQR) for these data?

16

A researcher finds that 12% of participants make between 3-5 visits to a physician each year. What are the real limits for this interval?

2.5-5.5

The following is a simple frequency distribution table. If we convert this frequency distribution to relative percentages, which of the following gives the corresponding percentages in each interval listed from the top down. Interval/Frequency. 44-46/6, 41-43/4, 38-40/5, 35-37/10, 32-34/5, total 30.

20%, 13%, 17%, 33%, 17%

A researcher selects a sample of 6 males and 11 females. She asks participants to rate the likelihood they would do female-stereotyped jobs (such as nursing or school teaching) on a scale from 1 = not likely at all to 5 = very likely. Men indicated that they would be less likely to do these jobs (M = 2.1) compared with women (M = 4.3). What is the weighted mean for this entire sample of 17 participants?

3.5

What is the percentile point at the 80th percentile in the following distribution? Frequency/Percentile Rank. 9-11/100%, 6-8/80%, 3-5/40%, 0-2/20%

8

A researcher records the sound (in decibels) during a series of lessons taught by a substitute teacher at a local elementary school. In his study, he found that the sound was 80±6 (M±SD) decibels. Assuming the data are normally distributed, which of the following is an appropriate conclusion?

95% of classes were between 68 and 92 decibels.

Fill in the missing values for A and B in this frequency distribution table: Interval/Frequency. 6.0-6.6/12, 5.3-5.9/7, 4.6-5.2/B, 3.9-4.5/10, A-3.8/8, total 50

A = 3.2, B = 13

Which of the following is true about the computational formula for variance?

It is a short-cut method for calculating variance when the population or sample size is large, it is derived mathematically from the definitional formula, The computational formula will always produce the same solution as the definitional formula (give or take rounding errors)., ALL OF THE ABOVE

A researcher records the following data: 4, 4, 4, 4, and 3. How would you describe the variability of these data?

It is very small (close to 0) because scores are approximately the same.

A researcher measures the amount of coffee consumed by college students while studying during the final exam week. In her study, she found that students drink 2.3±0.8 (M±SD) cups of coffee per study session. Assuming the data are normally distributed, which of the following is the most appropriate conclusion?

Most students drink between 1.5 and 3.1 cups of coffee per study session.

The size of a population is symbolized as ________, whereas the size of a sample is symbolized as ________.

N; n

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 the largest variance?

Sample A

State the problem with this simple frequency distribution. Interval/Frequency. 8-10/4, 6-8/7, 4-6/3, 2-4/6, 0-2/9.

The class intervals overlap.

(4 pts) A researchers measures the following heights (in inches) of CEO's selected at random: 72, 75, 75, 66, 64, 79, 79, 75, 70, 72, 75, 77, 77, 74. Which measure of central tendency is most appropriate for describing these data? Why? (Hint: Draw the shape of this distribution first).

The median. AND Because it is negatively skewed.

A researcher reports that "the average shopper in the sample (n = 12) purchased $65.00 worth of items (μ = $65.00) during a busy shopping day." What mistake was made is this citation?

The sample mean is written using the wrong notation.

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.

(2 pts) Describe SS (Sum of squares) in words. (Be sure you are complete, including all parts of this definition).

The sum of the squared deviations from the mean. (Or "Sum of the squared deviations of scores from the mean.").

(2 pts) When is the weighted mean equal to the arithmetic mean for combining the mean for two or more samples?

When the sample sizes (or the "weights") are equal.

A researcher wants to determine how many participants will take less than 24 seconds to complete a cognitive performance task. If he constructs a frequency distribution for these data, what type of distribution would be most appropriate to answer his question?

a cumulative frequency distribution from the bottom up

Which of the following will decrease the value of the mean?

adding a score below the mean

(Extra credit!!!! (2 pts). The degrees of freedom for the sample variance

are equal to the sample size minus one

(Extra credit!!!! 2 pts) What terms refer to each of the following measures, respectively: mean, median, and mode.

average, middle, and most

The use of tables and graphs to summarize data is an example of

descriptive statistics

The scale of measurement a researcher uses

determines the type of inferential statistics that can be done

A researcher selects a sample of 24 participants and has them complete a survey on dating preferences. In this example, what are the degrees of freedom for sample variance and what does this figure represent?

df = 23; it represents the number of scores that are free to vary in a sample.

A therapist observes that spouses are more likely to forgive their partners for lying to them if they find out the truth from their spouse and not a third party. In this example, the dependent variable is

forgiveness

Procedures that allow researchers to infer or generalize observations made with samples to the larger population from which they were selected best describes

inferential statistics

In the stem-and-leaf display, each number to the right of the vertical line is referred to as a ________; the numbers to the left of the vertical line are called the ________.

leaf; stem

A researcher records the time (in seconds) that participants arrive late for a scheduled research study. Assuming these data are normally distributed, which measure of central tendency is most appropriate to describe these data?

mean

The ________ is the middle value in a distribution of scores that are listed in numeric order.

median

(2 pts) Can variability be negative?

no

(4 pts) List the names of the four scales of measurement in order from least informative to most informative.

nominal, ordinal, interval, ratio

The correct order of operations in math, is:

parentheses, roots, exponents, multiplication, division, addition, and subtraction

A cumulative percentage summary that indicates the percentage of scores at or below a given value is called a

percentile rank

Each of the following is an example of quantitative data, except

political affiliation

A researcher compares the amount of college debt (in dollars) that undergraduate students incur up to their four-year degree. College debt is on what scale of measurement?

ratio

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

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

A researcher asks participants to estimate the height (in inches) of a statue that was in a waiting area. The researcher records the following estimates: 40, 46, 30, 50, and 34. If the researcher removes the estimate of 40 (say, due to an experimenter error), then the value of the mean will____ (Hint: Calculate the mean first!)

remain the same

A researcher records the time it takes to complete a memory task in a sample of 25 participants. He finds that the average participant completed the test in 43 seconds. The average time to complete this task is called a(n)

sample statistic

Researchers measure data in a ________ to learn more about individuals in the larger _______ of interest.

sample; population

Bar charts are a lot like histograms, except

the bars displayed in the graph do not touch

Which of the following best describes an independent variable?

the manipulated variable

Which of the following best describes a dependent variable?

the measured behavior

You are interested in measuring the construct, reinforcement. Which of the following measures for this construct is quantitative and continuous?

the size of a reward in grams

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

two

When would a researcher calculate a population mean?

when data are measured for all members of a population

Each deviation in the numerator for variance is squared because

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

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