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T-Test Tool
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T-Test Tool

Most descriptive comparisons in NCES reports are tested using Student's t statistic. Statistical significance is determined by calculating t values for differences between pairs of means or proportions and comparing these with published values of t for two-tailed hypothesis testing, using a 5 percent probability of a Type I error (a significance level of .05).

Student's t values may be computed to test the difference between estimates with the Independent Estimate t-Test Tool below. Note that this formula is valid only for independent estimates (e.g., it is not appropriate for comparing a total percentage with that for a subgroup that is included in the total).

Independent Estimate t-Test Tool

Estimate 1:
Estimate 2:
Standard Error 1:
Standard Error 2:

t value:

The difference in independent estimates is statistically significant at the p < .05 level if the t value displayed above is greater than 1.96.