Normal Distributions Use Table

The length of life of a chip clip is 24 months with a standard deviation of 4 months. Find the percentage of chip clips that will last less than 21 months. Round the the nearest hundredth place and do not include the % sign.

Books in the library are found to have average length of 350 pages with standard deviation of 100 pages, and follow a normal distribution. What percentage of books at that library are less than 80 pages?

• 35%

• .0035

• .35%

• 47.61%

A survey was conducted where 150 high school students were asked the average amount of time they spent doing household chores in one week. The data collected resulted in a mean time of 180.5 minutes with a standard deviation of 5.5 minutes. Which of these represents a 95% confidence interval for the mean weekly hours spent doing household chores of all high school students?

• [171.5, 189.5]

• [175, 186]

• [178.3, 182.8]

• [179.6, 181.4]

A scientist planted two groups of seedlings. After six months, she found that the heights for both groups were normally distributed with means and standard deviations as follows: Group A: Mean = 41.7 cm, Standard Deviation = 2.2 cm Group B: Mean = 38.6 cm, Standard Deviation = 3.4 cm For which group does a z-score of 1.5 give a taller plant?

• Group A - 45 cm

• Group A - 43.2 cm

• Group B - 43.7 cm

• Group B - 42 cm

Use the image of the normal graph provided. What percent of values are less than 46?

• 16%

• 84%

• 46%

• 12.5%

• 15.87%

• 15.39%

• 9.68%

• 84.61%

• 99.04%

• 0.96%

• 98.93%

• 97.68%

The mean and standard deviation of a population are 200 and 20, respectively. 
What is the probability of selecting 25 data values with a mean less than 190?

• 69%

• 0.6%

• 31%

• 99%

The mean and standard deviation of a population are 200 and 20, respectively. 
What is the probability of selecting 100 data values with a mean greater than 202?

• 45%

• 36%

• 25%

• 16%

Find the Z-score.

Mean = 21

Standard Deviation: 1.3

x = 22

• 0.77

• 5.33

• 1.07

• 1.26