Q: A company wants to estimate the mean monthly sales of its product. They take a random sample of 50 months and calculate a sample mean of $$\10$$,000$$ with a sample standard deviation of $$\$$2,000. $$What is the 95% confidence interval for the true mean monthly sales?

$$10,000 \pm 1.96 \times \dfrac{2,000}{\sqrt{50}}$$

Q: A factory produces light bulbs, and the probability that a bulb is defective is $$0.05. If 20 $$bulbs are tested, what is the probability that exactly 2 bulbs are defective? (Assume binomial distribution)

$$\binom{20}{2} \times 0.05^2$ \times 0.95$$^{18}$$

Q: A sample of 100 students has a mean test score of 75 and a standard deviation of 10. What is the 99% confidence interval for the mean score?

$$75 \pm 2.576 \times \dfrac{10}{\sqrt{100}}$$

Question 1

Which of the following statements best describes the concept of probability according to the Kolmogorov axioms?

Accepted Answer

Probability is a measure that assigns a value between 0 and 1 to events, with the probability of the entire sample space equal to 1.

Question 2

A company wants to estimate the mean monthly sales of its product. They take a random sample of 50 months and calculate a sample mean of $$\10$$,000$$ with a sample standard deviation of $$\$$2,000. $$What is the 95% confidence interval for the true mean monthly sales?

Accepted Answer

$$10,000 \pm 1.96 	imes \dfrac{2,000}{\sqrt{50}}$$

Question 3

Which of the following is a property of the normal distribution?

Accepted Answer

Its mean, median, and mode are all equal.

Question 4

A factory produces light bulbs, and the probability that a bulb is defective is $$0.05. If 20 $$bulbs are tested, what is the probability that exactly 2 bulbs are defective? (Assume binomial distribution)

Accepted Answer

$$\binom{20}{2} 	imes 0.05^2$ 	imes 0.95$$^{18}$$

Question 5

Which formula correctly represents the sample mean $$\bar{x}$$ for a dataset with $$n$$ observations $$x_1$$, $$x_2$$, ..., x_n$$?

Accepted Answer

$$\bar{x} = \dfrac{\sum_{i=1}^{n} x_i}{n}$$

Question 6

A business analyst wants to test if the average time to deliver a product is less than 5 days. Which statistical test should be used if the population standard deviation is unknown and the sample size is small?

Accepted Answer

One-sample t-test for the mean

Question 7

Which of the following best describes the correlation coefficient $$r$$?

Accepted Answer

It measures the strength and direction of a linear relationship between two variables.

Question 8

A regression analysis between advertising spend ($$X) $$and sales ($$Y) $$yields the equation $$Y = 500 + 20X. $$What is the interpretation of the coefficient 20?

Accepted Answer

For each additional unit spent on advertising, sales increase by 20 units.

Question 9

Which of the following is NOT a property of the binomial distribution?

Accepted Answer

The number of successes can exceed the number of trials.

Question 10

A company wants to compare the average productivity of two departments. Which statistical method is most appropriate?

Accepted Answer

Two-sample t-test

Question 11

If the sample mean is $$\bar{x} = 100$$ and the sample standard deviation is $$s = 15$$ for a sample of $$n = 25$$, what is the standard error of the mean?

Accepted Answer

$$\dfrac{15}{\sqrt{25}}$$

Question 12

Which of the following statements about hypothesis testing is correct?

Accepted Answer

The null hypothesis is rejected if the p-value is less than the significance level.

Question 13

A sample of 100 students has a mean test score of 75 and a standard deviation of 10. What is the 99% confidence interval for the mean score?

Accepted Answer

$$75 \pm 2.576 	imes \dfrac{10}{\sqrt{100}}$$

Question 14

Which of the following is the formula for the variance of a sample?

Accepted Answer

$$s^2$$ = \dfrac{\sum_{i=1}^{n} (x_i - \bar{x}$$)^2$$}{n-1}$$

Question 15

A business wants to know if there is a significant relationship between employee satisfaction and productivity. Which statistical technique should be used?

Accepted Answer

Correlation analysis

Question 16

Which of the following is a key assumption of the normal distribution?

Accepted Answer

The data are symmetrically distributed around the mean.

Question 17

A sample of 40 employees has a mean salary of $$\50$$,000$$ and a standard deviation of $$\$$8,000. $$What is the margin of error for a 90% confidence interval for the mean salary?

Accepted Answer

$$1.645 	imes \dfrac{8,000}{\sqrt{40}}$$

Question 18

Which of the following best describes the logic of hypothesis testing?

Accepted Answer

It involves comparing sample data to a hypothesized population parameter and making a decision based on the probability of observing the sample data.

Question 19

In a regression analysis, which formula is used to calculate the slope $$b of $$the regression line?

Accepted Answer

$$b = \dfrac{\sum (x_i - \bar{x})(y_i - \bar{y})}{\sum (x_i - \bar{x})^2$}$$

Statistics for Business: Key Topics and Study Guide

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드