# Statistics Fundamentals -CFI Quiz Answer

Statistics Fundamentals introduces the foundational concepts needed to run a statistical test and interpret the results. We will overview the two branches of statistics–descriptive statistics and inferential statistics—and run hypothesis tests on real and simulated data sets using Excel’s Data Analysis ToolPak.

The empirical rule is commonly used in which branch of statistics?

- Descriptive statistics
**Inferential statistics**- All of the above

The distribution of returns on U.S. bonds (a conservative investment) would be best described as:

**Normal**- Negative-skewed
- Right-skewed
- Leptokurtic
- Platykurtic

**3**

The graph below is most accurately described as being:

- Mesokurtic
**Positive-skewed**- Platykurtic
- Negative-skewed
- A histogram

Which visualization is useful for visualizing the correlation between two variables?

- Box-and-Whisker chart
- Bar chart
- Line graph
**Scatter plot**- Histogram

When comparing two samples of different sizes in Excel, which option should you select from the Data Analysis tool?

- T-test: Paired Two Sample for Means
- T-test: Two-Sample Assuming Unequal Variances
**T-test: Two-Sample Assuming Equal Variances**- T-test: Unpaired Two Sample for Means

A company has an NPS score of 42. The scores have a variance of 125. What is the standard deviation?

**√(125)**- 2.48
- 125²
- 2.98

When conducting a hypothesis test, the sample size needed can vary based on the population you are studying. However, as a rule of thumb, what is the minimum sample size we should use for a one-tail or two-tail test?

- 10% of your population
- √(variance)
- 150
**30**

The Central Limit Theorem tells us _________ trends towards ________ as our sample size grows.

- any measure of central tendency; normality
**the distribution of sample means; the normal distribution**- the sample mean; the population mean
- the normal distribution; the population’s distribution

The alpha value is equal to _____________ and describes the expected rate of _________.

- The statistical power; type II errors
- The confidence interval; type II errors
- The confidence level; type II errors
**1 – confidence level; type I errors**- The confidence level – beta; type I errors
- 1 – power; type I errors

How can we reduce the chances of a type I error (false positive)?

- Increasing our sample size
- Increasing our alpha
**Reducing our beta**- All of the above

Which of the following are examples of p-hacking? (Select all that apply).

Increasing your sample gradually until your test results reject the null hypothesis.

- Removing outliers after conducting the hypothesis test to see if it changes your results.
**Trying the test again with a new sample to see if it becomes more significant.****Changing around variables to see if your test results change.**- Conducting your test using a confidence value of 89 or below.

About 5 months ago, your company launched new branding for its video content. You believe the new branding to be more engaging than the old branding. To measure this, you want to run a Hypothesis test that compares the ‘Average Percent Viewed’ of both the old and new brand. The brand-style is identified under the “Brand’ column.

The data needed is located in your download files for this course. The file is labeled 04-Exam-ABTest-Data.csv. Include all samples in your hypothesis test.

Run this test in Excel. You’ll use your results to answer the following questions.

Conduct a t-test. Use the data provided in the 04-Exam-ABTest-Data.csv.

Your confidence level for this test will be at 95%.

What is the p-value for our test?

**0.003134**- 0.001446
- 0.001567
- 0.002892

About 5 months ago, your company launched new branding for its video content. You believe the new branding to be more engaging than the old branding. To measure this, you want to run a Hypothesis test that compares the ‘Average Percent Viewed’ of both the old and new brand. The brand-style is identified under the “Brand’ column.

The data needed is located in your download files for this course. The file is labeled 04-Exam-ABTest-Data.csv. Include all samples in your hypothesis test.

Run this test in Excel. You’ll use your results to answer the following questions.

Our confidence level is 95%. Based on the results of our t-test, how will we conclude our test?

- reject the alternative hypothesis
- fail to reject the alternative hypothesis
**reject the null hypothesis**- fail to reject the null hypothesis

About 5 months ago, your company launched new branding for its video content. You believe the new branding to be more engaging than the old branding. To measure this, you want to run a Hypothesis test that compares the ‘Average Percent Viewed’ of both the old and new brand. The brand-style is identified under the “Brand’ column.

The data needed is located in your download files for this course. The file is labeled 04-Exam-ABTest-Data.csv. Include all samples in your hypothesis test.

Run this test in Excel. You’ll use your results to answer the following questions.

The difference between our samples is statistically significant.

To describe the effect size of the new branding, we decide to run the Cohen’s d calculation. Using the results of the test and the standard deviation of our old branding, calculate the effect size.

Which of the following **best **describes our effect size?

- medium
- huge
**small**- large