How do you calculate 95 confidence interval in SAS?
For SAS coding, you cannot directly specify the confidence level, C, however, you can specify alpha which relates to the confidence as such, alpha = 1 – C, so for 95% we specify alpha = 0.05. So the 95% C.I. for µ is (87.3, 100.03).
How do you compare two means in SAS?
To compare the means of two groups in SAS, you can use either the TTEST procedure or the ANOVA procedure. The null hypothesis is that there is no difference in mean between the two groups.
Which Proc Ttest option would you use to change the confidence level in a confidence interval plot?
PERGROUP
requests plots of confidence interval for means. For a two-independent-sample design, you can specify one of the following options: TYPE=PERGROUP….PROC TTEST Statement.
| Option | Description |
|---|---|
| Basic Options | |
| ALPHA= | Specifies 1 – confidence level |
| DIST= | Specifies distributional assumption (normal or lognormal) |
| H0= | Specifies null value |
How do you check for equal variance in SAS?
To determine which of the two formulas to use, we first test the null hypothesis that the population variances of the two groups are equal. The test for equality of variances is based on the distribution of the ratio of the variances and uses the F statistic, F = s12/s22.
What kind of test for means will be produced when using PROC Ttest using a VAR statement and no other statements?
t-test
If a var statement is not specified, proc ttest will conduct a t-test on all numerical variables in the dataset. h. DF – The degrees of freedom for the single sample t-test is simply the number of valid observations minus 1. We loose one degree of freedom because we have estimated the mean from the sample.
Is the difference in the 95% confidence interval statistically significant?
The 95% confidence interval for the difference does not include 0, therefore the difference is statistically significant. By changing the value of the QUANTILE= option, you can compare quantiles other than the median.
What are the confidence limits for mean differences and standard deviation?
Confidence limits for means and standard deviations are shown in Figure 93.5. For the mean differences, both pooled (assuming equal variances for males and females) and Satterthwaite (assuming unequal variances) 95% intervals are shown. The confidence limits for the standard deviations are of the equal-tailed variety.
How to compare quantiles other than median in SAS?
By changing the value of the QUANTILE= option, you can compare quantiles other than the median. No other SAS procedure provides that level of control over quantile estimation. PROC QUANTREG provides another tool for the SAS programmer who needs to analyze quantiles.
What are the confidence intervals (CIs) for the quantiles?
The output shows that the confidence intervals (CIs) for the quantiles are similar, although the QUANTREG intervals are slightly wider. Although UNIVARIATE can produce CIs for these data, the situation changes if you add a weight variable.