3.5 Quiz 6: the normal distribution

Given X ~ N (300, 15), find P(280<X<340).

• A

  0.2000

• B

  0.7460

• C

  0.9050

• D

  0.9999

Given X ~ N(300, 15), find the 70th percentile.

• A

  0.5244

• B

  210.00

• C

  307.87

• D

  324.96

Given X ~ N(300, 15), what can be said of the median?

• A

  The mode = median and the mode = the mean.

• B

  It is the same as the mode.

• C

  It is less than the average.

• D

  It is the same as the average.

Given X ~ N(300, 15), the area to the right of x = 330...

• A

  is the same as the area to the right of z = 2.

• B

  P(X>330) is the same as the area to the right of z = 2 AND to the left of X = 270.

• C

  is the same as the area to the left of x = 270.

• D

  is the same as the area to the left of x = 330.

Given X ~ N(300, 15), find the Interquartile Range (IQR).

• A

  0.50

• B

  310.12

• C

  20.24

• D

  289.99

Given X ~ N(300, 15), find the z-score associated with x = 290.

• A

  15/10

• B

  -10

• C

  10/15

• D

  -10/15

For what do we use z-scores?

• A

  Because of the use of technology, there is no longer any use for z-scores.

• B

  to standardize scores from two or more different normal distributions so that we may compare the scores.

• C

  to help us calculate uniform and exponential probabilities.

• D

  to make our calculations easier because the mean = 0.

Given that X ~ N(10, 2), X>20...

• A

  cannot happen.

• B

  can happen 1/5 of the time.

• C

  is very unlikely to occur.

• D

  we cannot determine its probability.

Given that X ~ N(10, 2) and Y follows the Exponential Distribution with a mean of 10, which of the following are correct?

• A

  The median for Y is greater than the median for X.

• B

  The median for Y is less than the median for X.

• C

  The percentiles for X and Y are also equal.

• D

  The median for X and Y are also equal.

For data that is normally distributed, is it possible for the standard deviation to be larger than the mean?

• A

  No.

• B

  Yes.

• C

  There is not enough information to determine.