03
Mar
95 Percent Confidence Interval Formula. I hope this was helpful. But the sample size is 1500 instead of 659. The sample size is n10 the degrees of freedom df n-1 9. Calculation of Margin of Error using below formula is as follows Margin of Error Za2 σ n 196 20 1000 196 203162.
To find the critical value or Z a2. Confidence level 1 a. Because the sample size is small we must now use the confidence interval formula that involves t rather than Z. For a more precise and more simply achieved result the MINITAB TINTERVAL command. The confidence level is set at 095 but 099 is included for comparative purposes. Where Z is the Z-value for the chosen confidence level X is the sample mean σ is the standard deviation and n is the sample size.
Because the sample size is small we must now use the confidence interval formula that involves t rather than Z.
From -196 to 196 standard deviations is 95. In this video I show you how to calculate a 95 confidence interval in excel. Now plugin this new sample size in the formula and calculate a 95 confidence interval. Compute the confidence interval by adding the margin of error from the proportion from Step 1 and subtracting the margin of error from the proportion78 11 8978 11 67 The 95 confidence interval is67 to89. X is the mean. Because the sample size is small we must now use the confidence interval formula that involves t rather than Z.