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STATDISK Links:  Install · List & Stats · Histograms · Box Plots · CI Critical Values

Icon StatDisk.exeClick Analysis, Probability Distributions, Student-t DistributionUse STATDISK to lookup critical t or critical z or critical χ2 values for confidence intervals.

Click a symbol: z critical for CI of proportion ·  critical t for CI for mean  ·  critical chi squared for CI for standard deviation

Find critical t for CI for mean for df = 185 and a confidence level of 95%

critical t for CI for mean is always a positive number.

Statdisk window1. After opening STATDISK

click Analysis

click Probability Distribution

click Student-t Distributions

to open a new window shown to the right

2. α = 1.00 – 0.95 = 0.05

3. Divide α by 2 so α ÷ 2 = 0.025

4. Enter 185 for "Degrees of Freedom"

5. Enter 0.025 for "Area to the RIGHT of the t score.

6. t alpha over 2, critical t for confidence interval of the mean= 1.973