Provide an appropriate response.

A nutritionist wants to conduct a study to validate the efficacy of an herb as an aid in weight loss. She randomly assigns half of a group of overweight persons to a treatment group who are given the herb with instructions as to use and a planned diet for six weeks. The other half of the group is given a placebo with the same instructions and same diet. None of the participants know to which group they belong. She weighs each subject on Friday of each week. What type of blinding is being used?

1. does not use blinding
2. triple-blind
3. single-blind
4. double-blind

2.Which of the following is not a property of variance?

1. The value of the variance is always positive or 0.
2. The sample variance is a biased estimator of the population variance.
3. The value of the variance is zero only when all of the data values are the same number.
4. The units of variance are the squares of the units of the original data

A set of data items is normally distributed with a mean of 500. Find the data item in this distribution that corresponds to the given z-score.

z = 2, if the standard deviation is 50.

Suppose you will perform a test to determine whether there is sufficient evidence to support a claim of a linear correlation between two variables. Find the critical values of r given the number of pairs of data n and the significance level .

n = 6, = 0.05