You Z-value looks fine, which you can use as the population standard deviation is known.
You are after the lower bound so
Remember as gets large
I'm looking over corrections for one of my midterms and ran into a few problems giving me weird Z-values from confidence intervals that don't exactly correspond to my Cumulative T Distribution Table.
How do I calculate the Z value required? The answer it gives me is Za/2=1.44 but I have no clue why and can't find "Za/2" anywhere in my notes to determine how all of this works.A sample of 19 eggs of the Atlantic Fairy Tern are each measured. The mean diameter is 3.34 cm. The actual population standard deviation of the diameter is 0.2 cm, what is the lower limit of an 85% confidence interval on the mean?
Thanks for the link but that's no good on a final haha. I have tables with values for a tail with areas of .10, .05, .1, .05, .005, etc. but not some weird in-between values like .075 and .02 and stuff like that. I would love to find out a formula for these but I can't find it anywhere.