Ch.3 Stats

A student union cafeteria worker checked the weight of ten half-pound bags of whole bean coffee and recorded the following weights in pounds: 0.48, 0.51, 0.47, 0.49, 0.49, 0.50, 0.52, 0.48, 0.49, 0.51. What is the standard deviation weight of this group of coffee bags?

0.015

Assuming a normal distribution of data, what is the probability of randomly selecting a score that is more than 2 standard deviations below the mean? A .05 B .025 C .50 D .25

0.025

A student union cafeteria worker checked the weight of ten half-pound bags of whole bean coffee and recorded the following weights in pounds: 0.48, 0.51, 0.47, 0.49, 0.49, 0.50, 0.52, 0.48, 0.49, 0.51. What is the z-score weight of this group of coffee bags?

0.38

A student union cafeteria worker checked the weight of ten half-pound bags of whole bean coffee and recorded the following weights in pounds: 0.48, 0.51, 0.47, 0.49, 0.49, 0.50, 0.52, 0.48, 0.49, 0.51. What is the mean weight of this group of coffee bags?

0.49

In a normal distribution, the sum of the probabilities of all scores below the mean is equal to ______. A. 1 B .33 C .50 D .64

0.50

Assuming a normal distribution of data, what proportion of scores would be found between 1 and 3 standard deviations above the mean? A 34% B 5% C 15.85% D 27%

15.85%

Given a normal distribution of scores with 95% of the scores centered about the mean between the scores of 32 and 48, what is the variance?

16

Given a normal distribution of scores with µ = 85 and σ = 17.5, what raw score lies at the upper boundary of the interval that includes scores within one standard deviation of the mean?

1=X-85/17.5= 102.5

Based on what you know about the empirical rule and z-scores, and assuming a normal distribution, what is the approximate percentile rank of a score that is associated with a z-score of 0?

50th

In a standard normal curve, what percentile corresponds to a z-score of 2.0?

98

Two distributions, A and B, have the same mean, but Distribution A has σ = 2.0 and Distribution B has σ = 4.0. Which distribution has the greatest spread? A. Distribution A has the greatest spread. B. Distribution B has the greatest spread. C. Both have the same spread. D. Cannot be determined without a graph.

Distribution B has the greatest spread.

Determine whether the following statement is true or false. If false, rewrite it as a correct statement: It is impossible to have a z-score of 0. A False. A z-score of 0 can occur 68% of the time B False. A z-score of 0 is a standardized score that is equal to the standard deviation C True D False. A z-score of 0 is a standardized score that is equal to the mean

False. A z-score of 0 is a standardized score that is equal to the mean

The mean for a math test is 65 and the standard deviation is 8.0. The mean for a history test is 32 and the standard deviation is 3.0. A student who took both tests scored 71 on the math test and 36 on the history test. On which test did the student have a better score?

History

The process of standardization converts _________. A All scores to percentiles B Individual scores from different distributions to standard scores which share a common distribution C Raw scores to percentile ranks D Standard scores to z-scores

Individual scores from different distributions to standard scores which share a common distribution

The mean of a distribution of scores is determined to be to the right of (higher than) the median. What does that suggest about the distribution? A. It is bimodal. B. It has a negative skew. C. More scores are above the mean than below. D. It is positively skewed.

It is positively skewed

If you were to randomly select a score (data point) from a normally distributed data set, it would be most likely to be close to the

Mean

Assuming a normal distribution of data, what proportion of scores would be found within 0.5 σ of the mean? A 34% B More than 34% C Less than 34% D 0.5 (68%)

More than 34%

The pattern of data that is symmetric around a midpoint and fairly accurately predicts reality is called a _______. A. Bell B. Skewed distribution C. Normal curve D. Standardized distribution

Normal Curve

Most distributions in nature tend to be ________ distributed.

Normally

The foundation of inferential statistics is the idea that ________. A. Variability increases with sample size B. Reality can be estimated using what we know about a bell-shaped curve C. Predictions can be based on data from biased samples D. Estimates can be based on testimonials if the sample is representative

Reality can be estimated using what we know about a bell-shaped curve

The mean of a normally distributed population is 75 with a standard deviation of 8. If someone has a z-score of 2, what does this mean?

S/he is two standard deviations above what is average, or the mean.

If you were to randomly select a score (data point) from a normally distributed data set, it would be least likely to be close to the

Tails

We are told that the mean, median and mode of a distribution of scores are not the same value. What else do we know about that distribution? A. It is positively skewed. B. The data are not normally distributed. C. It is negatively skewed. D. Cannot say without more information.

The data are not normally distributed.

The first step in calculating a z-score is calculating which of the following?

The difference between a particular score and the population mean

In order to compare an individual score to a distribution, we need to convert which of the following? A The raw score into a standard score B The score to another distribution C The distribution to raw scores D The score to a raw score

The raw score into a standard score

Two students from two different schools recently took a science test. The first student correctly answered 34 questions on the test and the second student correctly answered 48 questions. What can you conclude from the two students' test scores? A The second student is smarter than the first student. B The two students did equally well on the exam. C The two students cannot be compared because there was no standardization procedure permitting appropriate comparisons. D The two students cannot be compared because the scores did not form a linear curve.

The two students cannot be compared because there was no standardization procedure permitting appropriate comparisons.

Which of the following best describes the normal curve? A. Unimodal, symmetric, and defined mathematically B. Bimodal, symmetric, and defined C. Multimodal and asymmetric D. Mathematically defined, bimodal, and symmetric

Unimodal, symmetric, and defined mathematically

If we wished to compare two scores that are measured on different scales, we would need to transform the scores into ______. A Standard deviations B Means C z-scores D Population parameters

Z scores

A ________represents the number of standard deviations a particular score is from the mean.A ______

z score