Changes to Mean and Standard Deviation

If we use the mean to measure the typical value or center of the data, we would use the _________ to measure the variability.

• IQR

• Median

• Mean

• Standard Deviation

In a population of five university students with GPAs of 2.5, 2.3, 1.7, 1.4, and 1.1, a sample of three students are considered. What would be the standard deviation of the resulting sampling distribution?

• 0.53

• 0.41

• 0.35

• 0.22

The mean of this data set is 17.8. What would happen to the mean if 40 was added to the data set?

• The mean would not change

• The mean would go up

• The mean would go down

The mean life of a tire is 30,000 km. The standard deviation is 2000 km.

Then, 68% of all tires will have a life between ___________ km and __________ km.

•  28,000 km and 32,000 km.

• 24,000 km and 34,000 km.

• 26,000 km and 34,000 km.

• 27,000 km and 31,000 km.

Approximately ​ (a)   of the data lies within 2 standard deviations of the mean.​

• 95%

• 50%

• 99.7%

• 68%

If this is the graph of data normally distributed with a mean of 30 and a standard deviation of 5, what label (number) is written at the blue circle?

• 40

• 35

• 45

• 50

Assume the average daily temperature for the first 30 days of March has a mean of 48 and a standard deviation of 8. If the temperature on March 31 is 62, then the standard deviation will...

• Go up

• Go down

• Stay the same

• Mean will decrease.

• Mean will increase.

• Mean will stay the same.

Approximately ​ (a)   of the data lies within 1 standard deviation of the mean.​

• 68%

• 50%

• 99.7%

• 95%

A quality control specialist at a glass factory must estimate the mean clarity rating for a new batch of glass using a sample of 18 glass sheets from the batch. Past investigations show that clarity ratings are normally distributed. The specialist decides to use a t-distribution rather than a z-distribution because ...

• The t distribution is more accurate than a z distribution.

• Clarity ratings for the entire bacth are normally distributed.

• The t-distribution will create a narrower interval than z.

• The standard deviation for the population is unknown.