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# AP statistics problem please help?

In a very large sample, if 10% of loaves weigh less than 15.34 ounces, and 20% weigh more than 16.31 ounces, what's the mean and standard deviation of the distribution of the weights of the bread?

### 3 Answers

- Awms ALv 71 decade agoFavorite Answer
On an AP stats class (and most of the time in real life), the phrase "in a very large sample" means that we should use the central limit theorem, so that the weights of the bread form a normal distribution.

Now let m be the mean and s be the standard deviation.

Then the two pieces of information tell us:

P( z < (15.34 - m) / s ) = .1

P( z < (16.31 - m) / s ) = .8

Looking at the z-tables, we find that approximately

(15.34 - m) / s = -1.28

(16.31 - m) / s = 0.84

Solve those equations for m and s to get

mean = 15.926

std dev = 0.4575

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- incorvaiaLv 43 years ago
recommend is basically general of the entire ability x1+x2+x3 /3 = x at the same time as median is the selection the place 0.5 of the numbers in that set is greater desirable and different 0.5 is smaller and occasion would be a million, 5 , 7, 9 , a hundred at the same time as median would be 7 with the aid of fact there are 2 greater desirable and 2 smaller selection interior the set at the same time as recommend would be sixty one. in situation 2 u have been given median velocity no longer recommend

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- efqyLv 71 decade ago
It's impossible to answer without substantially more assumptions than given here.

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