stats review

A researcher has participants choose between three advertisements. She finds that 54 prefer Ad A, 86 prefer Ad B, and 60 prefer Ad C. The probability or proportion of participants preferring Ad B is ______. Select one or more: a. 0.60 b. 86 c. 0.43 d. 0.86

.43

A therapist goes through her records and finds that 200 of her 400 patients showed significant improvement in mental health over the past year. Hence, the probability of her patients showing significant improvement in mental health is ______. Select one or more: a. 200 b. 0.05 c. 400 d. 0.50

.50

Five scatterplots are shown below. For the scatterplot in the middle, the Pearson correlation coefficient is likely to be ___.

0

A researcher records the following scores for an Olympic gymnast following her routine: 9.9, 9.8, 9.6, 9.5, 9.7, 9.1, 8.9, and 9.8. What is the range for the scores? Select one or more: a. 0.3 b. It is impossible to calculate the range with decimals. c. 0.5 d. 1.0 Feedback

1

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? Select one or more: a. 10 b. 6 c. There is not enough information to answer the question. d. 16

16

Based on the figure below, about what percentage of the population obtain a score between 12 and 20?

47.5

A researcher records the following scores: 1, 2, 5, 7, and 10. In terms of these data, the sum of squared differences of scores from their mean is _____. Select one or more: a. 5 b. 0 c. 25 d. 54

54

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? Select one or more: a. 7.1 b. 48 c. 6.9 d. 50

7.1

A researcher records 17 scores. What is the median position of these scores? Select one or more: a. it's not possible to know this without the raw scores b. the average of the 8th and 9th scores in numeric order c. the 9th score in numeric order d. the average of the 9th and 10th scores in numeric order

The correct answer is: the 9th score in numeric order

A researcher selects a sample of 6 men and 11 women. 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 the combined sample of 17 total participants? Select one or more: a. 4.3 b. 2.1 c. 3.2 d. 3.5

The correct answer is: 3.5

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? Select one or more: a. No; the mode is larger than the mean. b. Yes. c. There is not enough information to answer this question. d. No; the mean is larger than the mode. Feedback Your answer is correct. The correct answer is: No; the mode is larger than the mean.

The correct answer is: No; the mode is larger than the mean.

A professor grades 120 research papers and reports that the average score was 80%. What do we know about the sum of the differences of these 120 scores from their mean of 80%? Select one or more: a. The sum of the differences is minimal. b. The sum of the differences is equal to zero. c. It is impossible to know without knowing each of the 120 scores. d. The sum of the differences is 80%, the same as the mean.

The sum of the differences is equal to zero.

The following definition is related to which of the following concepts: procedures typically used to quantify measured behaviors and allows for the clear presentation of data summaries. Select one or more: a. Descriptive Statistics b. Inferential Statistics c. Recombinant Statistics d. Hypothesis Testing

a. Descriptive Statistics

Why is it important to divide by df to compute sample variance? Select one or more: a. Doing so makes the sample variance an unbiased estimator of the population variance. b. It is not important; there is no advantage for dividing by df. c. Doing so minimizes the likelihood that the sample variance will be a negative value. d. Doing so ensures that the value for sample variance varies between 0 and 1.

a. Doing so makes the sample variance an unbiased estimator of the population variance.

The mean is an appropriate measure of central tendency for Select one or more: a. data in which the mean, median, and mode are equal. b. data that are on an interval or ratio scale. c. all of these. d. data that are normally distributed.

all of these

Which of the following is consistent with the empirical rule? Select one or more: a. All of these. b. At least 95% of all scores lie within two standard deviations of the mean. c. At least 99.7% of all scores lie within three standard deviations of the mean. d. At least 68% of all scores lie within one standard deviation of the mean.

all of these

Bar vs. Histogram

bar has space, histogram smushed together

Which of the following statements is true? Select one or more: a. In the standard normal distribution, the shape of the distribution is asymmetrical if folded at the mean. b. In the standard normal distribution, the shape of the distribution is asymptomatic for convergence. c. In the standard normal distribution, z scores above the mean are positive and z scores below the mean are positive. d. In the standard normal distribution, z scores above the mean are positive and z scores below the mean are negative.

d. In the standard normal distribution, z scores above the mean are positive and z scores below the mean are negative.

Each deviation in the numerator for variance is squared because Select one or more: a. this inflates the value for variance, making it more accurate. b. without squaring each deviation, the solution for SS would be zero, and without squaring each deviation, the solution could be negative. c. without squaring each deviation, the solution for SS would be greater than positive one. d. without squaring each deviation, the solution for SS would be zero.

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

What I.Q. score is associated with the threshold for an individual being in the top 10%? Most I.Q. measures have a mean of 100 and a standard deviation of 15. The Unit Table cumulative percentage value of 0.90 equals a z-score of 1.28. Select one or more: a. 135 b. 110 c. 125 d. 119.2

d.119.2

The variance and standard deviation can never be Select one or more: a. larger than the mean. b. smaller than the mean. c. negative. d. zero.

negative

The median would be used to describe which of the following variables? Select one or more: a. ethnicity b. gender c. rankings d. brand name

rankings

Which measure tells how dispersed or spread out a distribution of scores? Select one or more: a. asymptote b. mode c. mean d. standard deviation

standard deviation

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? Select one or more: a. No; the median is larger than the mean. b. Yes. c. No; the mean is larger than the median. d. There is not enough information to answer this question.

yes

What terms refer to the meaning of each of the following measures, respectively: mean, median, and mode? Select one or more: a. average, middle, and most b. middle, most, and average c. average, most, and middle d. most, average, and middle

The correct answer is: average, middle, and most

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 a. population mean. b. median split. c. modal mean. d. sample mean.

The correct answer is: sample mean.

Which of the following statements is not true about effect size? Select one or more: a. Effect size measures the strength and direction of the linear relationship between two factors. b. Effect size is the difference between two means expressed in standard deviation units. c. Effect size is calculated using Cohen's d, where d = (M1 - M2)/SD. d. Effect size describes the strength of a statistical relationship.

a. Effect size measures the strength and direction of the linear relationship between two factors.

The university accepts prospective students based on their performance on either the ACT or SAT. The ACT and SAT means and standard deviations are 21 +/-5.4 and 500 +/-100, respectively. If Juanita obtained an ACT score of 23 and Juan obtained a SAT score of 560, which prospective student scored higher on the entrance examination? Select one or more: a. Juan scored higher on the entrance exam. b. Juan and Juanita obtained the same z-score and, therefore, their performance on the entrance examination is the same. c. Juanita scored higher on the entrance exam. d. The two scales have different means and standard deviations and, therefore, the two scores cannot be compared. This is why schools typically require either the ACT or the SAT, not one or the other.

a. Juan scored higher on the entrance exam.

Which of the following statements is not true about outliers? Select one or more: a. Outliers are extreme scores that are much higher or much lower than the rest of the scores in a distribution. b. Outliers may represent errors or misunderstandings, such as an equipment malfunction or confusion on the part of a participant. c. Outliers sometimes represent truly extreme scores on some variable of interest. d. Outliers are the result of the asymptotic function at each extreme tail of a normal distribution.

d. Outliers are the result of the asymptotic function at each extreme tail of a normal distribution.