Math Problem Statement

You observe a portfolio for five years and determine that its average return is

12.0112.01​%

and the standard deviation of its returns is

19.2819.28​%.

Would a​ 30% loss next year be outside the​ 95% confidence interval for this​ portfolio?

Question content area bottom

Part 1

The low end of the​ 95% prediction interval is

enter your response here​%.

​(Round to two decimal​ places.)

Part 2

Would a​ 30% loss next year be outside the​ 95% confidence interval for this​ portfolio?  ​(Select the best choice​ below.)

A.

​Yes, you can be confident that the portfolio will not lose more than​ 30% of its value next year. This is because the low end of the prediction interval is less than

minus−​30%.

B.

​Yes, you can be confident that the portfolio will not lose more than​ 30% of its value next year. This is because the low end of the prediction interval is greater than

minus−​30%.

C.

​No, you cannot be confident that the portfolio will not lose more than​ 30% of its value next year. This is because the low end of the prediction interval is greater than

minus−​30%.

D.

​No, you cannot be confident that the portfolio will not lose more than​ 30% of its value next year. This is because the low end of the prediction interval is less than

minus−​30%.

Solution

To answer this question, we need to calculate the 95% confidence interval based on the given information.

Step 1: Understanding the confidence interval

The 95% confidence interval is given by: Confidence Interval=Mean±1.96×Standard Deviation\text{Confidence Interval} = \text{Mean} \pm 1.96 \times \text{Standard Deviation} Where:

  • The mean return of the portfolio is 12.01%.
  • The standard deviation is 19.28%.

Step 2: Calculate the lower and upper bounds of the 95% confidence interval

Lower Bound=12.01%1.96×19.28%\text{Lower Bound} = 12.01\% - 1.96 \times 19.28\% Upper Bound=12.01%+1.96×19.28%\text{Upper Bound} = 12.01\% + 1.96 \times 19.28\%

Let me compute that.The 95% confidence interval for the portfolio's returns is:

  • Lower bound: -25.78%
  • Upper bound: 49.80%

Part 1: The lower end of the 95% prediction interval is -25.78% (rounded to two decimal places).

Part 2: Would a 30% loss next year be outside the 95% confidence interval?

A 30% loss means a return of -30%. Since the lower bound of the interval is -25.78%, a -30% return is lower than the lower bound. Therefore, it would fall outside the 95% confidence interval.

Thus, the correct answer is:

D. No, you cannot be confident that the portfolio will not lose more than 30% of its value next year. This is because the low end of the prediction interval is less than -30%.


Would you like more details or further clarification?

Here are five related questions you may find useful:

  1. How is a confidence interval constructed in statistics?
  2. What does the 95% confidence interval mean in practical terms?
  3. How do changes in the standard deviation affect the confidence interval?
  4. What is the significance of a 1.96 Z-score in confidence intervals?
  5. How can a portfolio's risk be mitigated if the confidence interval suggests potential large losses?

Tip: A wide confidence interval suggests high uncertainty in predictions, so diversifying your portfolio might help reduce the risk.

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Math Problem Analysis

Mathematical Concepts

Statistics
Confidence Intervals
Z-Scores

Formulas

Confidence Interval = Mean ± 1.96 * Standard Deviation

Theorems

Z-Score for a 95% Confidence Interval

Suitable Grade Level

Undergraduate Finance/Statistics