**Question 3.2**

A survey found that students at U.S. universities, on average, have a GPA of 3.342 with a standard deviation of 0.9. If 19 students are randomly selected, what is the probability that their mean GPA is at least 3.8? Leave your answer exactly as it is calculated in the calculator.

The probability that their GPA has a mean of at least 3.8 is

**Question 3.3**

Full-time Ph.D. students receive a stipend average of $15,837 per year with a standard deviation of $1600 find the probability that 25 full time PhD students make between $15,000 and $16,500.

The probability that 25 full time PhD student receive a stipend between $15,000 and $16,500 is

**Question 5.2**

A survey of 300 people between the ages of 18 and 25, showed that they spend, on average, $137.23 on entertainment each month. The population standard deviation is known to be $31.44. Construct a confidence interval for the mean amount of money people 17 to 25 spend on entertainment each month. Use a confidence level of 99%. Write your answer EXACTLY as is given by Excel. Do not round.

The lower limit is $ A

The upper limit is $ B

**Question 6.1**

Construct a confidence interval using a sample of size 15, with a sample standard deviation of 1.45, a sample mean of 5.3, and a confidence level of 90%. Write your answer EXACTLY as is given by Excel. Do not round.

The lower limit is A

.The upper limit is B

**Question 7.2**

In a Gallup poll of 2870 randomly selected adults, 64% said that they played video games at least twice a week. Construct a 95% confidence interval estimate for the proportion of adults who play video games twice a week. Write your answer EXACTLY as is given by Excel. Do not round.

The lower limit is A

.

The lower limit is B

**Question 8.1**

A researcher wants to investigate the number of hours a week a typical college student dedicates to study. From past studies, we know that the standard deviation of similar studies is 3.1 hours. How many students should be surveyed if we want to be accurate within 0.5 hours. Use a 95% confidence level. Write your answer EXACTLY as is given by Excel. Do not round.

We need to survey a minimum of A

students.

**Question 8.2**

An advertising company wants to investigate the mean number of hours spent by an adult (40 and older) using Facebook. How many adults 40 and older need to be surveyed by this company? From past studies, we know that the standard deviation is 4.2 hours. We want to be accurate within 1 hour. Use a confidence level of 90%. Write your answer EXACTLY as is given by Excel. Do not round.

The company needs to survey a minimum of A

adults (40 and older).

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Ans 3.2{:[" Ans "3.2],[mu=3.342","quad sigma=0.9],[P( bar(x)⩾3.8)=P[(( bar(x))-mu)/(6//sqrtn)⩾(3.8-3.342)/(0.9//sqrt9))],[=P(z⩾0.51)],[P( bar(x)⩾3.8)=1-P(z < 2.21)],[P( bar(x)⩾3.8)=1-0.986=0.014],[P( bar(x)⩾3.8)]:}Ans 3.3{:[3P(15000 leqslant bar(x)leqslant16500)q ... See the full answer