stat 200 lab quiz 6

The time taken for a computer to boot up, X, follows a normal distribution with mean 30 seconds and standard deviation 5 seconds. What is the standardized score (z-score) for a boot-up time of x =20 seconds?

-2.0

Assuming a standard normal distribution is appropriate and using Standard Normal Table, what is the approximate probability that a z-score is greater than or equal to 2.33? Said another way, what is P(Z ≥ 2.33)?

.01

For a normal random variable (Using Standard Normal Table), the probability of an observation being less than the median is:

.50

Scores on an achievement test had an average of 70 and a standard deviation of 10. Serena's score was 85. Using Standard Normal Table and assuming the scores have approximately a normal distribution, about what proportion of students scored lower than Serena?

.93

Use software to answer the following: You just found out that you have been kicked out of your apartment (through no fault of your own!) and need to find a new place to live. Suppose monthly rent for an individual is a normally distributed random variable with a mean of 334 dollars and a standard deviation of 22 dollars. What is the probability that you will find an apartment that costs more than 400 dollars per month.

0.001350

Use software to answer the following: You just found out that you have been kicked out of your apartment (through no fault of your own!) and need to find a new place to live. Suppose monthly rent for an individual is a normally distributed random variable with a mean of 334 dollars and a standard deviation of 22 dollars. What is the probability that you will find an apartment that costs less than 300 dollars per month.

0.061118

Suppose that the money spent by students at PSU on a Friday night is a normal random variable with a mean of 25 dollars and a standard deviation of 2 dollars. Using Standard Normal Table, find the probability that a student will spend more than 28 dollars on a Friday night.

0.0668

Using Standard Normal Table, find the probability that a z-score is less than -2.56 or greater than 1.51.

0.0707

Using Standard Normal Table, find P(-0.1 < Z < 0.5).

0.2313

Use software to answer the following: You just found out that you have been kicked out of your apartment (through no fault of your own!) and need to find a new place to live. Suppose monthly rent for an individual is a normally distributed random variable with a mean of 334 dollars and a standard deviation of 22 dollars. What is the probability that you will find an apartment that costs more than 350 dollars per month.

0.233529

Heights of college women have a distribution that can be approximated by a normal curve with a mean of 65 inches and a standard deviation equal to 3 inches. Using Standard Normal Table, about what proportion of college women are between 65 and 68 inches tall?

0.3413

The average time taken to complete an exam, X, follows a normal probability distribution with mean = 60 minutes and standard deviation 30 minutes. Using Standard Normal Table, what is the probability that a randomly chosen student will take at least an hour to complete the exam?

0.5000

Use software to answer the following: You just found out that you have been kicked out of your apartment (through no fault of your own!) and need to find a new place to live. Suppose monthly rent for an individual is a normally distributed random variable with a mean of 334 dollars and a standard deviation of 22 dollars. What is the probability that you will find an apartment that costs less than 350 dollars per month.

0.766471

Use software to answer the following: You just found out that you have been kicked out of your apartment (through no fault of your own!) and need to find a new place to live. Suppose monthly rent for an individual is a normally distributed random variable with a mean of 334 dollars and a standard deviation of 22 dollars. What is the probability that you will find an apartment that costs more than 300 dollars per month.

0.938882

Use software to answer the following: You just found out that you have been kicked out of your apartment (through no fault of your own!) and need to find a new place to live. Suppose monthly rent for an individual is a normally distributed random variable with a mean of 334 dollars and a standard deviation of 22 dollars. What is the probability that you will find an apartment that costs less than 400 dollars per month.

0.998650

Verbal SAT scores have approximately a normal distribution with mean equal to 500 and standard deviation equal to 100. The 95th percentile of z-scores is z = 1.65. What is the 95th percentile of verbal SAT scores?

665

You are applying to graduate schools and need to take the Graduate Record Examination (GRE). The quantitative (math) portion of this exam is a normal random variable with a mean of about 600 and standard deviation of 150. What score on this quantitative section of the GRE do you need in order to fall in the 67th percentile?

666

The average time taken to complete an exam, X, follows a normal probability distribution with mean = 60 minutes and standard deviation 30 minutes. Using Standard Normal Table, by what time should 67% of the students have finished the exam? (i.e. What is the 67th percentile for X?)

73.2 minutes