No, because $$12 \u003c 8.5 + (1.5 \times 3) = 13$$

$$X = 75 + (1.645 \times 10) = 91.45$$

Question 1

A researcher records the number of hours 8 students slept before an exam: 3, 5, 6, 7, 7, 8, 9, 12. What is the mean ($$\bar{x}) of $$these data?

Accepted Answer

$$\bar{x} = 7.125$$

Question 2

Given the same sleep data: 3, 5, 6, 7, 7, 8, 9, 12. What is the Interquartile Range (IQR)?

Accepted Answer

$$	ext{IQR} = 3$$

Question 3

Using the 1.5 $$	imes$$ IQR rule, is the value 12 a suspected outlier in the sleep data? (IQR = 3, $$Q_3 = 8.5$)

Accepted Answer

No, because $$12 \u003c 8.5 + (1.5 	imes 3) = 13$$

Question 4

If the standard deviation of student sleep hours is $$s = 2.67$$, which interpretation is correct?

Accepted Answer

On average, students' sleep hours differ from the mean by about 2.67 hours.

Question 5

Exam scores are normally distributed with $$\mu = 75$$ and $$\sigma = 10. $$What percentage of students scored between 55 and 95?

Accepted Answer

95%

Question 6

A student scored 88 on the exam. What is their Z-score?

Accepted Answer

$$Z = \frac{88 - 75}{10} = 1.3$$

Question 7

Using Table A, what proportion of students scored higher than an 88? (Z = 1.3)

Accepted Answer

$$1 - 0.9032 = 0.0968$$

Question 8

What score would a student need to be in the top 5% (95th percentile) of test-takers? ($$\mu = 75$$, $$\sigma = 10$$, $$Z \approx 1.645)$$

Accepted Answer

$$X = 75 + (1.645 	imes 10) = 91.45$$

Question 9

A bag contains 30% Red, 20% Blue, and 50% Green marbles. What is the probability of picking a marble that is not Green?

Accepted Answer

$$1 - 0.50 = 0.50$$

Question 10

If you pick two marbles with replacement, what is the probability both are Red?

Accepted Answer

$$0.30 	imes 0.30 = 0.09$$

Question 11

You sample 50 marbles and find 28% are Red. Which number is the parameter ($$p) $$and which is the statistic ($$\hat{p}$$)?

Accepted Answer

Parameter $$p = 0.30$$, Statistic $$\hat{p} = 0.28$$

Question 12

In a medical study testing a new blood pressure medication, what is the explanatory variable and what is the response variable?

Accepted Answer

Explanatory: Medication; Response: Blood Pressure

Question 13

You are given random digits: 95592 94007 69971 91481 60779. If subjects are labeled 01–40, which two numbers are selected first?

Accepted Answer

29 and 40

Question 14

How would you implement a Block Design using 'Age' as the blocking variable in the medical study?

Accepted Answer

Split subjects into two groups by age (50), then randomly assign medication/placebo within each group.

Question 15

Why is a Block Design better than a Completely Randomized Design in this medical study?

Accepted Answer

It reduces variation caused by age, making treatment effects easier to detect.

Question 16

In the context of the medical study, what is the difference between a Single-Blind and Double-Blind experiment?

Accepted Answer

Single-Blind: Subjects do not know their treatment; Double-Blind: Neither subjects nor experimenters know.

Question 17

After entering data in a list on the TI-84 calculator, which menu do you use to find the mean and standard deviation?

Accepted Answer

1-Var Stats

Question 18

Which TI-84 command finds the area under the curve between two Z-scores?

Accepted Answer

normalcdf

Question 19

If you are given an area of 0.25 (the 25th percentile) and asked to find the Z-score, which TI-84 command do you use?

Accepted Answer

invNorm

Step-by-Step Guidance for Statistics Midterm Practice Exam

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