Normal Dist- Z-scores, Probability, CLT

What is the purpose of z-scores?

• to describe where you are in relation to the mean

• to find the mean of the distribution

• to describe the shape of the distribution

• to find the standard deviation of the distribution

The sign of the z-score indicates whether the location is above(positive) or below(negative) the mean.

• True

• False

Find the z-score value corresponding if the location is BELOW the mean by 2 standard deviations.

Hint: Don't over think this. Remember the mean is 0.

• +2.00

• -2.00

• +1.25

• -1.00

The mean temperature in Glens Falls for the month of February is 23 degrees with a standard deviation of 4.2 degrees. Approximately what percent of days in February will have days below 23 degrees?

(Remember to move the decimal for a percentage)

(6.3 Notes)

• 5%

• 34%

• 50%

• 68%

The shelf life of a particular dairy product is normally distributed with a mean of 12 days and a standard deviation of 3 days.

About what percent of the products last 6 days or less?

(6.3 Notes)

• 68%

• 34%

• 16%

• 2.3%

The mean and standard deviation of a population are 400 and 40, respectively. Sample size is 25.

What is the mean of the sampling distribution? (6.5 Notes)

• 400

• 40

• 25

• 8

The mean and standard deviation of a population are 400 and 40, respectively. Sample size is 25.

What is the standard deviation you would type in the calculator? (6.5 Notes)

• 400

• 40

• 25

• 8

Suppose the teenagers that attend public high schools get an average of 5.7 hours of sleep each night with a standard deviation of 1.7 hours. What is the probability that a randomly selected group of 35 high school students get more than 6 hours of sleep each night?

(6.5 Notes)

• .430

• .148

• .281

• .087

Red blood cell counts of women are normally distributed with a mean of 4.577 and a standard deviation of 0.382. Find the probability that one randomly selected woman has a red blood cell count above 5.4.

(6.3 Notes)

• 0.150

• 0.0156

• 0.215

• 0.0237

Red blood cell counts of women are normally distributed with a mean of 4.577 and a standard deviation of 0.382. If 25 women are randomly selected, find the probability that the mean of their red blood cell counts is less than 4.444.

(6.5 Notes)

• 0.409

• 0.0409

• 0.368

• 0.0368