Tests of µ, Standard Deviation Estimated (3 of 4)

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  1. In the fifth step, the probability computed in Step 4 is compared to the significance level stated in Step 2. Since the probability value (0.025) is less than the significance level (0.05) the effect is statistically significant.

  2. Since the effect is significant, the null hypothesis is rejected. It is concluded that the mean reading achievement score of children in the city in question is higher than the population mean.

  3. A report of this experimental result might be as follows:
    The mean reading-achievement score of fifth grade children in the sample (M = 80.85) was significantly higher than the mean reading-achievement score nationally (µ = 76), t(19) = 2.44, p = 0.025.
    The expression "t(19) = 2.44" means that a t test with 19 degrees of freedom was equal to 2.44. The probability value is given by "p = 0.025." Since it was not mentioned whether the test was one- or two- tailed, a two-tailed test is assumed.

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