## How do you compare two means in SAS?

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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.

## 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 does Pr (> F mean?**

Pr > F – This is the p-value associated with the F statistic of a given source. The null hypothesis that the predictor has no effect on the outcome variable is evaluated with regard to this p-value.

### What does PR t mean in SAS?

Pr > |t| – The p-value is the two-tailed probability computed using the t distribution. It is the probability of observing a t-value of equal or greater absolute value under the null hypothesis.

### What is PR T SAS?

The ttest procedure performs t-tests for one sample, two samples and paired observations. The single-sample t-test compares the mean of the sample to a given number (which you supply).

**What is nway SAS?**

The NWAY options instructs the SUMMARY procedure to only create rows with a combination of all class variables. These options are available only when used with the CLASS statement, not with the BY statement.

#### What is the logistic function in SAS?

The LOGISTIC function in SAS ® is the inverse of the logit link function 1/ (1+e -LogOdds) Because this is not a linear combination of the model parameters or of the LS-means, you cannot use the ESTIMATE or LSMESTIMATE statements to estimate the difference in differences of means.

#### Why do we use F < the critical value in SAS?

We will rely on SAS to perform this test and will not expect you to look up these critical values. F < the critical value so we do not reject the null hypothesis that the variances are equal and thus can use the pooled standard error.

**How to calculate the difference in difference of means between probabilities?**

(For an ordinary regression model, it estimates the difference in difference of means). If you want to estimate the difference in difference of probabilities, then you need to apply the inverse of the logit link to obtain each probability. This can be done with either the NLEstimate macro or using the ESTIMATE statement in PROC NLMIXED.

## What is the p-value for the F test using SAS?

The p-value for the F test using SAS is not significant at α=0.05 (p = 0.9446), so we do not reject H0: σ 12 = σ 22