The mean of a normal probability distribution is 320; the standard deviation is 18.
a)About 68% of the observations lie between what two values? Value #1_____. Value #2______.
b)About 95% of the observations lie between what two values? Value#1_____. Value#2_____.
c)Practically all of the observations lie between what two values? Value#1______. Value#2______.
Answer:
Given,
mean = 320 &
Standard deviation( sd) =16
a)
Since from the standard definition,
we know that the about 68% of the values fall between 1 SD of the mean
so interval is 320 16
= (320 - 16, 320+16)
= (304,336)
so they fall between 304 and 336
b)
68% of the values fall between 2 SD of the mean
= 320 16*2
= (320 32)
= (320-32, 320+32)
= (288 ,352)
c)
practically all the values fall within 3 Standard deviation of mean
320 16*3
= 320 48
= (320 - 48, 320+48)
= (272 , 368)
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