Question

Choose the correct answer.

1. What is the percentile rank of 60 in the distribution of N(60, 100)?

a. 10

b. 50

c. 60

d. 100

1. The skewness value for a set of data is +2.75. This indicates that the distribution of scores is which one of the following?

   1. Highly negatively skewed

   2. Slightly negatively skewed

   3. Symmetrical

   4. Slightly positively skewed

   5. Highly negatively skewed

2. For a normal distribution, all percentiles above the 50th must yield positive z-scores. Is this true or false?

3. The distribution of variable X has a mean of 10 and is positively skewed. The distribution of variable Y has the same mean of 10 and is negatively skewed. Are the medians for the two variables the same or different?

Answer 1

Choose the correct answer.

1. What is the percentile rank of 60 in the distribution of N(60, 100)?

a. 10

Answer: b. 50

c. 60

d. 100

Note: for normal distribution median is same as mean. Percentile rank of 60( median) is 50.

The skewness value for a set of data is +2.75. This indicates that the distribution of scores is which one of the following?

Highly negatively skewed

Slightly negatively skewed

Symmetrical

Slightly positively skewed

Answer: Highly positively skewed

Note: If the skewness is less than -1 or greater than 1, the data are highly skewed. +2.75 is positive and greater than 1.

For a normal distribution, all percentiles above the 50th must yield positive z-scores. Is this true or false?

True:

Note: data values above 50^th percentiles are greater than mean value. Therefore for data values above mean, the z scores are positives.

The distribution of variable X has a mean of 10 and is positively skewed. The distribution of variable Y has the same mean of 10 and is negatively skewed. Are the medians for the two variables the same or different?

The medians for the two variables are different.

X is positively skewed, therefore median is smaller than mean value of 10.

Y is negatively skewed, therefore median is larger than mean value of 10 .