Standard Normal Distribution. Find the indicated z score. The graph depicts the standard normal distribution of bone density scores with mean 0 and standard deviation 1.

Short Answer

Expert verified

The z-score indicated in graph is 0.82.

Step by step solution

01

Given information

The bone density score follows the standard normal distribution with a mean of 0 and a standard deviation of 1.

02

Describe the z-score

The z-score is the distance along the horizontal scale of the standard normal distribution (corresponding to the number of standard deviations above or below the mean). These are the values taken by the standard normal distribution, represented by Z.

03

State the relationship between the area and the probability

As the standard normal curve has an area of 1 enclosed under the curve, the area has a one-to-one correspondence with the probability.

The left-tailed area is equal to the cumulative probabilities, which are obtained by using the standard normal table (Table A-2) for z-scores.

To find the required right-tailed area, subtract the cumulative probabilities from 1.

04

Find the z-score

The area represented is mathematically represented as

Areatotherightofz=PZ>z0.2061=1-PZ<zPZ<z=1-0.2061PZ<z=0.7939

The z-score that has the area of 0.7939 to the left of it is obtained from the standard normal table as follows.

From the standard normal table, the area of 0.7939 is observed corresponding to the row value of 0.8 and the column value of 0.02, which implies that the z-score is 0.82.

Thus, the indicated z-score value with the right-tailed area of 0.2061 is 0.82.

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Most popular questions from this chapter

In Exercises 5–8, find the area of the shaded region. The graphs depict IQ scores of adults, and those scores are normally distributed with a mean of 100 and a standard deviation of 15 (as on the Wechsler IQ test).

Significance For bone density scores that are normally distributed with a mean of 0 and a standard deviation of 1, find the percentage of scores that are

a. significantly high (or at least 2 standard deviations above the mean).

b. significantly low (or at least 2 standard deviations below the mean).

c. not significant (or less than 2 standard deviations away from the mean).

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In Exercises 11–14, use the population of {34, 36, 41, 51} of the amounts of caffeine (mg/12oz) in Coca-Cola Zero, Diet Pepsi, Dr Pepper, and Mellow Yello Zero.

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b. Compare the mean of the population {34, 36, 41, 51} to the mean of the sampling distribution of the sample mean.

c. Do the sample means target the value of the population mean? In general, do sample means make good estimators of population means? Why or why not?

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