Math Problem Statement

Both of your confidence interval limits are incorrect. The confidence interval for the estimate of

muμ

is

x overbar minus Upper E less than mu less than x overbar plus Upper Ex−E<μ<x+E​,

where E is the margin of​ error, and

x overbarx

is the sample mean. The margin of error is given by the formula​ below, where

t Subscript alpha divided by 2tα/2

is the critical t value separating an area of

alpha divided by 2α/2

in the right tail of the Student t​ distribution, and

dfequals=nminus−1

is the number of degrees of freedom.

Upper E equals t Subscript alpha divided by 2 Baseline times StartFraction s Over StartRoot n EndRoot EndFraction left parenthesis Use df equals n minus 1 right parenthesisE=tα/2•sn   (Use df=n−1)

If using a table of critical​ t-values to find a critical value of

t Subscript alpha divided by 2tα/2​,

but the table does not include the number of degrees of​ freedom, the closest value could be​ used, the next lower number of degrees of freedom found in the table could be used as a conservative​ value, or interpolation could be used.

​Alternatively, technology can be used to find the confidence interval. Make sure to round to one decimal place.

Solution

Thank you for the clarification. Let's recalculate the 90% confidence interval for the mean pulse rate of adult females using the t-distribution.

Steps for Calculation

  1. Calculate the sample mean (xˉ\bar{x}) and sample standard deviation (ss) for the female pulse rates.
  2. Determine the critical t-value (tα/2t_{\alpha/2}) for a 90% confidence interval with df=n1df = n - 1.
  3. Compute the margin of error (EE).
  4. Construct the confidence interval.

Step 1: Calculate the Sample Mean and Sample Standard Deviation

Pulse rates for females: 79, 87, 85, 81, 80, 77, 76, 86, 74, 95, 90, 64, 89, 92, 66, 72, 62, 84, 65, 64, 60, 74, 55, 68, 67, 67, 57, 77

Calculate the Mean (xˉ\bar{x}):

xˉ=xin=209628=74.9\bar{x} = \frac{\sum x_i}{n} = \frac{2096}{28} = 74.9

Calculate the Sample Standard Deviation (ss):

s=(xixˉ)2n110.2s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n-1}} \approx 10.2

Step 2: Determine the Critical t-Value

For a 90% confidence interval with df=n1=27df = n - 1 = 27, the critical t-value (tα/2t_{\alpha/2}) can be found using a t-table or a calculator. For 27 degrees of freedom and a 90% confidence level, t0.051.703t_{0.05} \approx 1.703.

Step 3: Compute the Margin of Error

E=tα/2sn=1.70310.2283.3E = t_{\alpha/2} \cdot \frac{s}{\sqrt{n}} = 1.703 \cdot \frac{10.2}{\sqrt{28}} \approx 3.3

Step 4: Construct the Confidence Interval

xˉE<μ<xˉ+E\bar{x} - E < \mu < \bar{x} + E 74.93.3<μ<74.9+3.374.9 - 3.3 < \mu < 74.9 + 3.3 71.6<μ<78.271.6 < \mu < 78.2

Final Answer

The 90% confidence interval for the mean pulse rate for adult females is:

71.6 bpm<μ<78.2 bpm71.6 \text{ bpm} < \mu < 78.2 \text{ bpm}

Would you like more details or have any questions? Here are five related questions you might want to explore:

  1. How do you calculate a confidence interval for a population proportion?
  2. What is the difference between a z-distribution and a t-distribution?
  3. How do you determine the sample size needed for a specific margin of error?
  4. What assumptions are necessary for constructing confidence intervals?
  5. How do you interpret confidence intervals in hypothesis testing?

Tip: Always ensure the sample data is randomly selected and representative of the population to make valid inferences.

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Math Problem Analysis

Mathematical Concepts

Statistics
Confidence Intervals
T-Distribution

Formulas

Confidence Interval Formula: x̄ - E < μ < x̄ + E
Margin of Error: E = tα/2 * (s / √n)

Theorems

Student's t-Distribution

Suitable Grade Level

Undergraduate