EPY-6214-Wei: Unit 1 Quizzes

For the population of scores shown in the frequency distribution table, the mean is____.

29/10 = 2.90

A normal distribution has a mean of u = 100 with a SD = 20. If one score is randomly selected from this distribution, what is the probability that the score will have a value between X = 80 and X = 100.

0.3413; find the z-score for both values and subtract the z-scores; then find the value that best fits.

What is the total number of scores for the distribution shown in the following table? X f 4 3 3 5 2 4 1 2

14; count the f column

A population has a mean of u = 30. If 3 points are added to each score, what is the mean for the new distribution?

33

The sum of the squared deviation scores is SS = 20 for a population of N = 5. What is the variance for this population.

4; variance for a population = SS/N

Which of the following statements is true for a distribution of data points?

50% of the scores are above the median.

A positive deviation always indicates a score that is less than the mean.

False

What kind of frequency distribution graph shows the frequencies as bars that are separated by spaces?

Bar graph

A set of exam scores forms a negatively skewed distribution, it suggests that the majority of the students did not score well on the exam.

False

For the distribution in the following table, the 90th percentile is X = 27.5. X c% 25-29 100% 20-24 80% 15-19 20%

False

For the following scores, ∑(X + 1)² = 81. Scores: 1, 3, 0, 1

False

For the following scores, ∑(X-1) = 10. Scores: 1, 3, 7

False

For the following scores, ∑X² = 49. Scores: 1, 4, 2, 0

False

The participant in a research study are classified as high, medium, or low in self-esteem. This classification involves measurement on a nominal scale.

False It is ordinal

Using the average score to describe a sample is an example of inferential statistics.

False inferential statistics is used to describe a population.

For a 100-point exam, a score of X = 65 is definitely above the median.

False; I dunno why

For a negatively skewed distribution, the mean usually has a larger value than either the median or the mode.

False; I dunno why

In a sample of n = 40, X = 31 corresponds to z = -1.50 and X = 39 corresponds to z = 0.50. The sample mean is M = 36.

False; I dunno why

A population with a u = 45 and s = 8 is standardized to create a new distribution with u = 100 and s = 20. In this transformation, a score of X = 41 from the original distribution will be transformed into a score of X = 110.

False; look back at calculations

For a sample with a standard deviation of s = 8, a score of X = 42 corresponds to z = -0.25. The mean for the sample is M = 40.

False; the z-score would be z = 0.25 with that data.

In a sample with s = 6, a score of X = 53 corresponds to z = -0.50. The mean for this sample is M = 50.

False; this z-score would be z = 0.50.

If one score is randomly selected from a normal distribution with u = 100 and SD = 20, the probability of obtaining a score greater than X = 110 is p = 0.6915.

False; you would look at the (C) Portion in Tail column and find that 0.3085 is the remanding portion.

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?

Sampling error

What additional information is obtained by measuring two individuals on an interval scale compared to an ordinal scale?

The size of the difference

A high school gym teacher records how much time each student requires to complete a one-mile run. This is an example of measuring a continuous variable.

True

A histogram is constructed so that adjacent bars touch.

True

If a researcher measures two individuals on a nominal scale, it is impossible to determine which individual has the larger score.

True

In a distribution with s = 20, a score that is above the mean by 10 points will have a z-score of z =0.50.

True

Students is an introductory art class are classified as art major and non-art majors. This is an example of measurement on a nominal scale.

True

To determine how much difference there is between two individuals, you must use either an interval or a ratio scale of measurement.

True

For a population, a deviation score is computed as X-u.

True; I dunno why

When the z-score value in a normal distribution is negative, the majority of the area is on the right-hand side of the distribution.

True; I dunno why

For a population with a standard deviation of s = 12, a z-score of z = 0.50 corresponds to a score that is above the mean by 6 points.

True; because standard deviation and z score are distance from the mean. 1/2 the distance from the mean would be 6.

A sample with a variance of 25 has a standard deviation equal to 5 points

True; because the standard deviation is the square root of the variance

A vertical line drawn through a normal distribution at z = 1.25 will separate the distribution into two sections. The proportion in the smaller section is 0.1056.

True; look up z-score in appendix B and find the Portion in Tail (C) value.

For any normal distribution, exactly 97.50% of the z-score values are less than z = 1.96.

True; you would look at the (B) Portion in Body column for z = 1.96 and find that 0.9750 is what falls behind in the body.

For a normal distribution with u = 100 and SD = 20, the score that separates the top 60% of the distribution from the bottom 40% is X = 95.

True; z = -0.25, look at Appendix B for lowest value (Portion in tail); use z-score to check the equation.

Any individual with a positive z-score has a score greater than the mean.

True; z-score is distance from the mean

For any normal distribution, exactly 97.50% of the z-score values are less than z = 1.96.

True; z-score is positive, so look at the Portion in Body (B) column to find what is behind the z-score.

Under what circumstances is a score that is 15 points above the mean an extreme score relatively far from the mean?

When the population SD is much smaller than 15; it's all about distance (SD) from the mean.

If the following continuous distribution was shown in a histogram, the bar above the 15-19 interval would reach from _____ to _____. X f 20-25 2 15-19 5 10-14 4 5-9 1

X = 14.5 to X = 19.5

A normal distribution has a mean of u = 24 with a SD = 3. What is the minimum score needed to be in the top 14% of the distribution.

X = 27.24; I dunno why

Scores on the SAT form a normal distribution with a mean of u = 500 with SD = 100. If the state college only accepts students who score in the top 60% on the SAT, what is the minimum score needed to be accepted.

X = 475; I dunno why

A normal distribution has a mean of u = 80 with SD = 20. What score separates the lowest 30% of the distribution from the rest of the scores?

X = 69.6; *Lowest* = Portion in tail; *lowest* = a negative z-score.

In a frequency distribution graph, frequencies are presented on the _____ and the scores (categories) are listed on the _____.

Y axis; X axis

If a variable can be divided into an infinite number of factional parts, then it is a(n) _____ variable.

continuous

Statistical methods that organize, summarize, or streamline data are called _____.

descriptive statistics

For a population with a mean of u = 40, a score of X = 37 corresponds to z = -0.50. The SD for the population is s = 3.

false; the SD is 6

For a negatively skewed distribution with a mode of X = 25 and a median of 20, what is the most likely value for the mean?

less than 20

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.

ordinal

Using letter grades (A, B, C, D, and E) to classify student performance on an exam is an example of measurement on a(n) _____ scale of measurement.

ordinal

A researcher uses an anonymous survey to investigate the study habits of American college students. The entire group of American college students is an example of a _____.

population

Which of the following symbols identifies the sample variance?

s2

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 _____.

sample: population

The normal distribution is

symmetrical

For a population with a standard deviation of SD = 6, what is the z-score corresponding to a score that is 12 points above the mean?

z = 2.00