Confidence Intervals and Sample Size

lu49076_ch07.qxd 5/20/2003 3:16 PM Page 338
338 Chapter 7 Confidence Intervals and Sample Size
TI-83 Plus
Step by Step
7–14
a) Select Calc>Column statistics.
b) Click the option for Standard deviation.
c) Enter C1 Assets for the Input variable and s for Store in:.
3. Select Stat>Basic Statistics>1-Sample Z.
4. Select C1 Assets for the Samples in Columns.
5. Click in the box for Standard Deviation and enter s. Leave the box for Test mean empty.
6. Click the [Options] button. In the dialog box make sure the Confidence Level is 90 and the
Alternative is not equal.
7. Optional: Click [Graphs], then select Boxplot of data. The boxplot of these data would
clearly show the outliers!
8. Click [OK] twice. The results will be displayed in the session window.
One-Sample Z: Assets
The assumed sigma = 14.4054
Variable N Mean StDev SE Mean 90% CI
Assets 30 11.0907 14.4054 2.6301 (6.7646, 15.4167)
Finding a z Confidence Interval for the Mean (Data)
1. Enter the data into L1. 2. Press STAT and move the cursor to TESTS.
3. Press 7 for ZInterval.
4. Move the cursor to Data and press ENTER.
5. Type in the appropriate values.
6. Move the cursor to Calculate and press ENTER.
Example TI7–1
This is Example 7–3 from the text. Find the 90% confidence interval for the population mean,
given the data values
12.23 2.89 13.19 73.25 11.59 8.74 7.92 40.22 5.01 2.27
16.56 1.24 9.16 1.91 6.69 3.17 4.78 2.42 1.47 12.77
4.39 2.17 1.42 14.64 1.06 18.13 16.85 21.58 12.24 2.76
The population standard deviation s is unknown. Since the sample size is n � 30, one can use
the sample standard deviation s as an approximation for s. After the data values are entered in L1 (step 1 above), press STAT, move the cursor to CALC, press 1 for 1-Var Stats, then press