A. Student study times. A class survey in a large class for first-year college students asked, "About how many hours do you study during a typical week?" The mean response of the 463 students
was Hx= 13.7 hours. Suppose that we know that the study time follows a Normal distribution with standard deviation o= 7.4 hours in the population of all first-year students at this university

A. Use the survey result to give a 99% confidence interval for the mean study time of all first-year students.

B. What condition not yet mentioned must be met for your confidence interval to be valid

A.  12.68 - 14.72 hours

B. Normal distribution.

Step-by-step explanation:

Part A

This question is using quantitative data. A 99% confidence interval means that you want to know the range where 99% of the population will be. To find this you have to convert the 99% CI into the z-score which is -2.58SD to + 2.58SD.  

Note that the standard deviation(SD) is from the sample, not the population. We still need to find the standard deviation of the population. The formula is:

population SD =

Where the o= sample SD = 7.4

n= number of sample = 463

The calculation will be:

population SD =

population SD = = 0.3951

The bottom limit will be:

Mean - SD * z-score= 13.7 - 0.3951*2.58 = 12.68 hours

The upper limit will be:

Mean + SD * z-score= 13.7 + 0.3951*2.58 =14.72 hours

The 99% CI range will be 12.68 - 14.72 hours

Part B

The table used to convert confidence interval into z-score depends on the distribution type of the data. Most data is classified as normal distributed, a data type that will concentrated at mean and spread equally from the mean. Normal distribution data will look like a bell which make it also called bell curve.  

The question tells you that the data is normal distribution, but that doesn't mean every data is normally distributed. There are a lot of other data distribution type so we have to do some tests to know the normality of the data in real-life data.

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2. angles qrt and qst both measures 156 degrees.

step-by-step explanation:  

we have been given a diagram of a circle and we are told that measure of arc qvt is 156 degrees.  

we can see from our given diagram that angle qrt and angle qst subtends to arc qvt.

since we know that angles subtended by the same arc at the circumference are always equal.

by angle subtended by same arc theorem, measure of angle qrt and angle qst will be equal to the measure of arc qvt.

therefore, angles qrt and qst both measures 156 degrees and 2nd statement is the correct choice.