My data had 110 individuals with a mean \bar{x} = 67.736 and a standard deviation s=4.176. Therefore, my standard error is
SE \approx s/\sqrt{n} = 4.176/\sqrt{110} = 0.398.
For a 95% confidence interval, I need a z^* multiplier of 2 to get
ME = 2\times0.398 = 0.796.
Thus, my confidence interval is
[67.736 - 0.796, 67.736 + 0.796] = [66.94, 68.532].
For a 99% level of confidence, the [normal calculator indicates that I need a z^* multiplier of 2.576. Thus, my margin of error is now
ME = 2.576\times0.398 = 1.02525
and myconfidence interval is
[67.736 - 1.02525, 67.736 + 1.02525] = [66.7108, 68.7613].
Here’s what I typed to produce this:
My data had 110 individuals with a mean $\bar{x} = 67.736$ and a standard deviation $s=4.176$. Therefore, my standard error is
$$
SE \approx s/\sqrt{n} = 4.176/\sqrt{110} = 0.398.
$$
For a 95% confidence interval, I need a $z^*$ multiplier of 2 to get
$$
ME = 2\times0.398 = 0.796.
$$
Thus, my confidence interval is
$$
[67.736 - 0.796, 67.736 + 0.796] = [66.94, 68.532].
$$
For a 99% level of confidence, the [normal calculator indicates that I need a $z^*$ multiplier of $2.576$. Thus, my margin of error is now
$$
ME = 2.576\times0.398 = 1.02525
$$
and myconfidence interval is
$$
[67.736 - 1.02525, 67.736 + 1.02525] = [66.7108, 68.7613].
$$