SOLUTION: Find the critical value z a/2 that corresponds to the given confidence level.
80%
z a/2 =
_ (Round to two decimal places as needed.)
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-> SOLUTION: Find the critical value z a/2 that corresponds to the given confidence level.
80%
z a/2 =
_ (Round to two decimal places as needed.)
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Question 1132703: Find the critical value z a/2 that corresponds to the given confidence level.
80%
z a/2 =
_ (Round to two decimal places as needed.) Answer by Theo(13342) (Show Source):
You can put this solution on YOUR website! confidence level = 80% = .8
alpha = 1 - .8 = .2
alpha / 2 = .1
that is the area to the left of the z-score on the low side of the confidence level and the area to the right of the z-score on the high side of the confidence level.
to find the area to the left of the low side z-score, you would look up an area of .1 in the z-score table and get the closest z-score.
to find the area to the right of the high side z-score, you would find the area of 1 - .1 = .9 in the z-score table and get the closest z-score.
the table tells you the area to the left of a z-score.
the unit digit and the first decimal digit of the z-score are in the row indicated by the left hand column.
the second decimal digit is in the column on that row indicated by the top row.
for example:
z-score of 1.28 would show 1.2 in the left hand column on the indicated row.
the .08 that is added to it to make 1.28 would show on the top row of the indicated column.
i found.
area of .89973 gave a z-score of 1.28
are of .90147 gave z-score of 1.29.
1.28 was the closest so i chose that.
area of .10027 gave a z-score of -1.28
area of .09853 gave a z-score of -1.29
-1.28 was the closest so i chose that.
since the normal distribution table is symmetric about the mean, i only needed to find the low side z-score.
the high side z-score would be the with with a revered sign.
the results of that inquiry are shown below.
i also used the following normal distribution calculator.
in this calculator, i chose to find the z-score from the area and put in an area of.8 (the confident level) and chose between.
it gave me the same answer with much less effort on my part and with greater accuracy.
note that an area of .8 was the confidence level and the area in between left an area of .1 to the left of it and an area of .1 to the right of it which was my alpha / 2 that i calculated earlier.
