Finding Mean and Standard Deviation of a Sample

To test a claim about a mean, when the population standard deviation is unknown we use:

• z procedures

• Pythagorean Theorem

• t procedures

• np > 10 and n(1-p) > 10

These symbols represent the mean and standard deviation for which of the following distributions?

• The Population

• The Sample

• The Sampling Distribution

The Gallup Poll asked a random sample of 1785 adults whether they attended church during the past week.  Let p-hat be the proportion of people in the sample who attended church.  A newspaper report claims that 40% of all U.S. adults went to church last week.  Suppose this claim is true. 
Calculate the standard deviation of the sampling distribution. 

• 0.0116

• 0.0117

• 0.0118

• 0.0119

The set of the weights of professional football players was found to have a mean of 275 lbs. with a standard deviation of 5 lbs. If there are a total of 1,650 pro football players in the US, what is the minimum number that weigh between 250 and 300 lbs.?

• 96%

• 75%

• 93.75%

• 88.89%

If test scores for a class are: 100, 100, 90, 90, 80, 80, 70, 70, 60, and 60, what are the mean and sample standard deviation?

• mean = 80, stdev = 14.9

• mean = 70, stdev = 14.9

• mean = 80, stdev = 13.9

• mean = 80, stdev = 12.9

• mean = 85, stdev = 14.9

Suppose the heights of adult men are normally distributed. The heights of a sample of 30 men are shown below in inches. Compute the mean of the sample.

• 71

• 70

• 69

• 68

The term "snowstorms of note" applies to all snowfalls over 6 inches. The snowfall amounts for snowstorms of note in Utica, New York, over a four-year period are as follows: 7.1, 9.2, 8.0, 6.1, 14.4, 8.5, 6.1, 6.8, 7.7, 21.5, 6.7, 9.0, 8.4, 7.0, 11.5, 14.1, 9.5, 8.6 What are the mean and population standard deviation for these data, to the nearest hundredth?

• mean = 9.46; standard deviation = 3.74

• mean = 9.46; standard deviation = 3.85

• mean = 9.45; standard deviation = 3.74

• mean = 9.45; standard deviation = 3.85

What is the sample mean and standard deviation for the following data:

• Mean 27.5, Standard deviation 19.7

• Mean 27.5, Standard deviation 21.6

• Mean 19.5, Standard deviation 8

• Mean 19.5, Standard deviation 21.6

Answer explanation

Here the 71 affected the mean and standard deviation. The median and IQR would be better measures to use here.

Way to look for the details!

These symbols represent the mean and standard deviation for which of the following distributions?

• The Population Distribution

• The Distribution of the Sample

• The Distribution of the Sample Means (Sampling Distribution)

The mean age of a dinosaur fossil in a particular fossil bed is 85 million years. The standard deviation of the fossil ages from this bed is 2.5 million years. At least __________ of fossils in this bed are between 80 and 90 million years old.

• 75 %

• 88.89 %

• 2%

• 70%