Confidence Intervals and Sample Size

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Summary
Finding a Confidence Interval for the Variance and Standard
Deviation (Data)
1. Enter the data values into L1. 2. Press PRGM, move the cursor to the program named SDINT, and press ENTER twice.
3. Press 1 for Data.
4. Type L1 for the list and press ENTER.
5. Type the confidence level and press ENTER.
6. Press ENTER to clear the screen.
Example TI7–3
This refers to Example 7–15 in the text. Find the 90% confidence interval for the variance
and standard deviation for the data:
59 54 53 52 51 39 49 46 49 48
Finding a Confidence Interval for the Variance and Standard
Deviation (Statistics)
1. Press PRGM, move the cursor to the program named SDINT, and press ENTER twice.
2. Press 2 for Stats.
3. Type the sample standard deviation and press ENTER.
4. Type the sample size and press ENTER.
5. Type the confidence level and press ENTER.
6. Press ENTER to clear the screen.
Example TI7–4
Section 7–6 Summary 359
This refers to Example 7–14 in the text. Find the 95% confidence interval for the variance and
standard deviation, given n � 20 and s � 1.6.
An important aspect of inferential statistics is estimation. Estimations of parameters of
populations are accomplished by selecting a random sample from that population and
choosing and computing a statistic that is the best estimator of the parameter. A good estimator
must be unbiased, consistent, and relatively efficient. The best estimators of m
and p are and , respectively. The best estimators of s2 and s are s2 X pˆ
and s, respectively.
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