Normal distribution

Adding 5 to all observations of a sample

• increases the mean by 5

• does not change the mean

• decreases the mean by 5

• changes the mean in an unpredictable way

Adding 5 to all observations of a sample

• Increases the standard deviation by 5

• does not change the standard deviation

• multiplies the standard deviation by 5

• changes the standard deviation in an unpredictable way

Multiplying all observations by 2

• increases the mean by 2

• multiplies the mean by 2

• does not change the mean

• change the mean in an unpredictable way

How large is the grey area?

• 0.1

• 0.5

• 1

• 2

How large is the probability that a random variable with standard normal distribution is between 0 and 2?

• approximately 0%

• approximately 25%

• approximately 48%

• approximately 98%

A person of our class is 1.65 m tall. We have a mean of 1.75 and a standard deviation of 0.05. What is the Z score of the height of the person?

• -2

• -1

• 0

• 1

Which normal distribution has the largest standard deviation?

• A

• B

• C

• D

What is the probability that a random variable with standard normal distribution is 0?

• 0

• approximately 0.05

• approximately 0.1

• 0.5

What do we know about the standard deviation of all Z scores of a sample?

• The standard deviation is 0

• The standard deviation is 1

• The standard deviation is smaller than the standard deviation of the original sample

• Nothing

Which of the boxplots shows a sample from a normal distribution?

• A

• B

• C

• D