Statistics and Probability Answers

If the correlational value is 0.19, this means?
Answer and rationalization:

A z-score of 3 is approximately how many standard deviations above the mean?
Answer and rationalization:

A z-score of 0 would correspond to approximately what percentile?
Answer and rationalization:

In a distribution where X=21 and S=3, what is the z-score?
Answer and rationalization:

If the score is equal to the mean, the z-score will be?
Answer and rationalization:

If you are given X=57 and S=4, what is the variance?
Answer and rationalization:

Within a quartile system, the 2nd quartile is the:
a. 20th percentile
b. 80th percentile
c. 50th percentile
d. 75th percentile
Answer and rationalization:

7. Suppose you are in the 87th percentile rank on a test. This means
a. You are among the 13 students in class
b. 87% of the students got a lower score than you
c. You got 87% of the test items correctly
d. 87% of the students got a score higher than you
Answer and Rationalization:

A sample of 150 people from a certain industrial community showed that 80 people suffered from a lung disease. A sample of 100 people from a rural community showed that 30 suffered from the same lung disease. At α =0.05, is there a difference between the proportions of people who suffer from the disease in the two communities?

Plasma-glucose levels are used to determine the presence of diabetes. Suppose the mean ln (plasma-glucose) concentration (mg/dL) in 35- to 44-year-olds is 4.86 with standard deviation = 0.54. A study of 100 sedentary people in this age group is planned to test whether they have a higher or lower level of plasma glucose than the general population.
a1. If the expected difference is 0.10 ln units, then what is the power of such a study if a two-sided test is to be used with α = .05?
a2. How many people would need to be studied to have 80% power under the assumptions in Problem a1?