Posted by **Sue** on Saturday, March 2, 2013 at 2:43pm.

Boxes of bran flakes are known to be normally distributed with a mean weight of 475g and a standard deviation of 10g.Calculate the probability of a box having a weight exceeding 485 grams. Calculate the probability that the mean weight of sixteen boxes will exceed 480g.

- statistics -
**MathGuru**, Saturday, March 2, 2013 at 5:34pm
Use z-scores.

Formula for the first part:

z = (x - mean)/sd

With your data:

z = (485 - 475)/10

I'll let you finish the calculation.

Once you have the z-score, check a z-table for the probability. (Remember the problem is asking "weight exceeding" 485 grams.)

Formula for the second part:

z = (x - mean)/(sd/√n)

With your data:

z = (480 - 475)/(10/√16)

I'll let you finish the calculation.

Once you have the z-score, check a z-table for the probability. (Remember the problem is asking "mean weight... will exceed" 480 grams.)

I hope this helps and will get you started.

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