Statistics and Probability Answers

What is the percentage of common variance between variables if the correlation

coefficient is -0,7?

1. 70%

2. 4,9%

3. -49%

4. 49%

In a Math test, the mean score is 42 and the standard deviation is 3. Assuming normality, what is the probability that the score picked will lie above score 50? *

Find the area under the normal curve for each z-score. Shade accordingly.

1. P( < 2.20)

2. P( -2.5 < z < 2.01)

A continuous random variable is normally distributed with a mean of 45 and standard deviation 0f 6. Illustrate the following notations in a normal curve.

P( 30 < X < 50 )

P( 33 ≤ X ≤ 39)

P( X < 57 )

A random variable X has a normal distribution with mean 45 and variance of 9.

Find the range of scores that lie:

a. within one standard deviation from the mean

b. within two standard deviations from the mean

scores on acommon final examination in alarge enrollment, multiple selection freshman course are normally distributed with a mean of 72. 7 and standard deviation of 13.1 a. Find the probability that the score X on a randomkly selected examination paper is between 70 and 80

C. Find the probabilities on a standard normal curve.

1. P(-3.0 ˂ z < -1.68)

2. P(-2.76 < z < 2)

3. P(1.53 < z < 2)

Find each of the following percentile points and draw the appropriate normal

curve. Complete your procedures.

1.The results of the entrance examination for freshmen are normally distributed with x=87 and s=12.5. What is the percentile rank of a score of 90?

We take a random sample of 60 households to estimate the percentage of all

homes in the Spring Town Village that have a refrigerator. It turns out that 49 of

the 60 homes in our sample have a refrigerator. Use 95% confidence level to

calculate the length of confidence interval estimation of population proportion of

households with refrigerator.