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Ch 2.2 Practice Problems:

1)The stem and leaf plot given is of the IQ test scores of 74 seventh graders.

The data represents a normal curve with a population mean of 111 and a

standard deviation of 11 (so this represents all of the seventh graders in the

Midwest).

*First sketch a normal bell curve and fill out the mean, and the

values 1, 2, and 3 standard deviations above and below the mean.

1) Between what values do the IQ scores of 95% of all rural

Midwest seventh graders lie?

2) What percent of the IQ scores for rural 3) What percent of all students have IQ scores

Midwest seventh graders are greater than 144 or higher? None of the 74 students in our

100? sample school had scores this high. Are you

surprised at this? Why?

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Ch 2.2 Practice Problems:

1)The stem and leaf plot given is of the IQ test scores of 74 seventh graders.

The data represents a normal curve with a population mean of 111 and a

standard deviation of 11 (so this represents all of the seventh graders in the

Midwest).

*First sketch a normal bell curve and fill out the mean, and the

values 1, 2, and 3 standard deviations above and below the mean.

1) Between what values do the IQ scores of 95% of all rural

Midwest seventh graders lie?

2) What percent of the IQ scores for rural 3) What percent of all students have IQ scores

Midwest seventh graders are greater than 144 or higher? None of the 74 students in our

100? sample school had scores this high. Are you

surprised at this? Why?

B) The distribution of heights of young woman aged 18 to 24 is approximately N(64.5, 2.5)

1) Sketch a normal density curve for the distribution of young woman’s heights. Label points 1, 2, and 3 standard deviations from the mean.

2) What percent of young women have heights greater than 67 inches? Show your work.

3. What percent of young women have heights between 62 and 72 inches? Show your work.

C) Determine if the following data is approximately normal: A survey of 20 daily travel time had these results (in minutes):

26, 33, 65, 28, 34, 55, 25, 44, 50, 36, 26, 37, 43, 62, 35, 38, 45, 32, 28, 34

Note: Use a graphing calculator to find the mean and standard deviation of the data.

B) The distribution of heights of young woman aged 18 to 24 is approximately N(64.5, 2.5)

1) Sketch a normal density curve for the distribution of young woman’s heights. Label points 1, 2, and 3 standard deviations from the mean.

2) What percent of young women have heights greater than 67 inches? Show your work.

3. What percent of young women have heights between 62 and 72 inches? Show your work.

C) Determine if the following data is approximately normal: A survey of 20 daily travel time had these results (in minutes):

26, 33, 65, 28, 34, 55, 25, 44, 50, 36, 26, 37, 43, 62, 35, 38, 45, 32, 28, 34

Note: Use a graphing calculator to find the mean and standard deviation of the data.

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