FORESTRY
AGRICULTURAL STATISTICS AND ECONOMICS
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]


1.65


1.96


2.58


2.33

Detailed explanation1: The Z value for 95% confidence is Z=1.96. [Note: Both the table of Zscores and the table of tscores can also be accessed from the “Other Resources” on the right side of the page.] What is the 90% confidence interval for BMI? (Note that Z=1.645 to reflect the 90% confidence level.)
Detailed explanation2: Zscores are equated to confidence levels. If your twosided test has a zscore of 1.96, you are 95% confident that that Variant Recipe is different than the Control Recipe.
Detailed explanation3: 1.96 is used because the 95% confidence interval has only 2.5% on each side. The probability for a z score below −1.96 is 2.5%, and similarly for a z score above +1.96; added together this is 5%.
Detailed explanation4: Z is the standard normal random variable. The table value for Z is the value of the cumulative normal distribution. For example, the value for 1.96 is P(Z<1.96) = . 9750.