Statistics Final Exam

In a normally distributed data distribution with a mean of 100 and a standard deviation of 10, what is the z-score that corresponds to the 90th percentile?

• 1

• 2

• 1.281551567

• 1.682163271

In a normally distributed data distribution with a mean of 100 and a standard deviation of 10, what is the interval centered around the mean in which 60% of all observations will fall?

• (91.58, 108.42)

• (90, 110)

• 102.53

• (89.12, 111.84)

In a normally distributed data distribution with a mean of 100 and a standard deviation of 10, what is the probability that a randomly selected observation will be greater than 120?

• .022750062

• .977249938

• .036581264

• .963418736

For a normally distributed data set, what is the probability that an observation is at least 2.2 deviations away from the mean? [You might begin by drawing a normal curve with a center between the endpoints z=-2.2 and z=2.2.]

• 2 x 0.0139

• 2 x 0.0212

• 2 x 0.0176

• .9722

Given a normally distributed data distribution, such as heights of a large population, suppose that a particular height is the 75th percentile. What would be the corresponding z-score for this height?

• 1

• .6744897495

• Not possible to determine

• .8151624982

Suppose an exam has an average of 59 and a standard deviation of 11. Assume the scores are approximately normally distributed. What is the approximate exam score for which only 18% scored higher?

• 69.07

• 72.12

• 55.67

• 75.54

What is the positive z-score for which 28% of normally distributed data will fall within z deviations of the mean? Also, if μ = 68 and σ = 11, then what number corresponds to z?

• .358, 71.943

• .401, 74.826

• .319, 68.394

• .396, 73.012

Suppose a restaurant finds its daily profits have a normal distribution with mean $140 and standard deviation $80. What is the probability that the restaurant loses money on any given day? That is, what is the probability that the profit is less than $0?

• 0.04

• 0.1

• 0.015

• 0.075

What word refers to our best guess for the parameter?   

• Confidence Interval

• Confidence Level

• Point Estimate

• Margin of Error

What is the z-score that corresponds to a 99% confidence interval?

• 2.62

• 2.58

• 2.68

• 2.72