|
|
|
||||
|
|
|||||
Figure 6.3, page 161. ztail and zdemo are available from ATS and can be downloaded over the Internet using the findit command (see How can I use the findit command to search for programs and get additional help? for more information about using findit).
zdemo 1.5 -1.5
ztail .1336 2
Z-score, page 163; figure 6.4, page 164. zcalc is available from ATS and can be downloaded over the Internet using the findit command (see How can I use the findit command to search for programs and get additional help? for more information about using findit).
zcalc 4.032 4 1.257 627
z-score for sample means
(m - mu) (4.032 - 4) (4.032 - 4)
z = ---------- = ---------------- = ----------------- = 0.64
s/sqrt(n) 1.257/sqrt(627) 0.0502
ztail .5222 2
Z-score, page 164. zcalc is available from ATS and can be downloaded over the Internet using the findit command (see How can I use the findit command to search for programs and get additional help? for more information about using findit).
zcalc 4.032 4 1.257 6270
z-score for sample means
(m - mu) (4.032 - 4) (4.032 - 4)
z = ---------- = ---------------- = ----------------- = 2.02
s/sqrt(n) 1.257/sqrt(6270) 0.0159
Confidence interval, page 165.
cii 627 4.032 1.257
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
| 627 4.032 .0501997 3.93342 4.13058
Z-score, page 166.
zcalc 3.01 0 7.309 29
z-score for sample means
(m - mu) (3.01 - 0) (3.01 - 0)
z = ---------- = ---------------- = ----------------- = 2.22
s/sqrt(n) 7.309/sqrt(29) 1.3572
Test for a single proportion, page 170; confidence interval, page 171.
prtesti 1227 .482 .5
One-sample test of proportion x: Number of obs = 1227
------------------------------------------------------------------------------
Variable | Mean Std. Err. z P>|z| [95% Conf. Interval]
---------+--------------------------------------------------------------------
x | .482 .0142648 33.7894 0.0000 .4540415 .5099585
------------------------------------------------------------------------------
Ho: proportion(x) = .5
Ha: x < .5 Ha: x ~= .5 Ha: x > .5
z = -1.261 z = -1.261 z = -1.261
P < z = 0.1036 P > |z| = 0.2073 P > z = 0.8964
cii 1227 .482
-- Binomial Exact --
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
| 1227 .4816626 .0142645 .4533704 .5100448
Z-score, page 178.
zcalc 4.17 4 1.39 2879
z-score for sample means
(m - mu) (4.17 - 4) (4.17 - 4)
z = ---------- = ---------------- = ----------------- = 6.56
s/sqrt(n) 1.39/sqrt(2879) 0.0259
Confidence interval using t, page 184.
cii 29 3.01 7.31
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
| 29 3.01 1.357433 .2294247 5.790575
Single-sample t-test, page 185.
ttesti 29 3.01 7.31 0
One-sample t test
------------------------------------------------------------------------------
| Obs Mean Std. Err. Std. Dev. [95% Conf. Interval]
---------+--------------------------------------------------------------------
x | 29 3.01 1.357433 7.31 .2294247 5.790575
------------------------------------------------------------------------------
Degrees of freedom: 28
Ho: mean(x) = 0
Ha: mean < 0 Ha: mean ~= 0 Ha: mean > 0
t = 2.2174 t = 2.2174 t = 2.2174
P < t = 0.9826 P > |t| = 0.0349 P > t = 0.0174
Power of a test, page 195. Stata uses the t-distribution rather than the z-distribution so the results below will differ slightly for the book value.
sampsi 0 10, alpha(.05) sd(18) n(36) onesample onesided
Estimated power for one-sample comparison of mean
to hypothesized value
Test Ho: m = 0, where m is the mean in the population
Assumptions:
alpha = 0.0500 (one-sided)
alternative m = 10
sd = 18
sample size n = 36
Estimated power:
power = 0.9543
UCLA Researchers are invited to our Statistical Consulting Services
We recommend others to our list of Other Resources for Statistical Computing Help
These pages are Copyrighted (c) by UCLA Academic Technology Services