Degrees of Freedom & Variance
Formula for degrees of freedom.
What is df = n - 1?
Formula for sample variance.
What is s2 = SS/(n-1) = SS/df?
The value that is expected for the t statistic when the null hypothesis is true.
What is 0?
The effect size (small, medium, or large) for r2 = 0.12.
What is a medium effect size?
Confidence interval for: M = 9, t = 3, sM = 1.5.
What is 9+- 4.5? What is 4.5, 13.5?
The degrees of freedom for n = 86.
What is df = 85?
Formula for estimated standard error.
What is sm = square root of (s2 / n)?
n required to assume a normal distribution.
What is n = 30?
The effect size (small, medium, or large) for r2 = .24.
What is a medium effect size?
Confidence interval. M = 16, t = 3.4, sM = 2.
What is mu = 16 +- 3.4(2)? What is 9.2, 22.8?
True or false: As sample size and df increase, the t distribution more closely resembles a normal distribution.
What is true?
Formula for estimated cohen's d.
What is (M - mu) / s?
Formula for the t statistic.
What is t = (M - mu) / sM?
r2 effect size. t = -2.67, n = 8.
What is r2 = .47?
Confidence interval. M = 86, t = 1.82, sM = 3.
What is 86 +- 5.46? What is 80.54, 91.46?
Estimated standard error: n = 9, SS = 72.
What is 1?
Formula for r2.
What is r2 = (t2) / (t2 + df)?
In this case, a t statistic should be used instead of a z-score.
What is when the standard deviation is unknown?
Effect size for Cohen's d = .11.
What is a small effect size?
Confidence interval for M = 46, sM = 1.5. t = -2.306 and 2.306.
What is mu = 46 - 3.459 and 46 + 3.459? What is 42.541, 49.459?
n = 9, SS = 288. Compute the sample variance and the estimated standard error for the sample mean.
What is s2 = 36 and sm =2?
Formula for confidence intervals.
What is mu = M + t(sM) and mu = M - t(sM)?
t = 2.30. Two-tailed test with .05 alpha level. The sample has to be at least n = ____ to reject the null.
What is n = 10?
Cohen'sd. population = 25, mu = 40. M = 44, s2 = 100.
What is .4?
90% confidence interval for mu. n = 4, M = 40, s2 = 16.
What is mu = 40 +- 2.353(2)