Normal Dist. Q: Assume that the weights of quarters are....

[Angel626]

Assume that the weights of quarters are normally distributed with a mean of 5.67 g and a standard deviation 0.070 g.

a. If a vending machine will only accept coins weighing between 5.428 g and 5.82 g, what % of legal quarters will be rejected?

b. If the quarters having weights in the lowest 0.5% and highest 0.5% weight range are to be rejected, what are the two cutoff weights?

 

[tkhunny]

Re: Help with Normal Distribution Question

Assume that the weights of quarters are normally distributed with a mean of 5.67 g and a standard deviation 0.070 g.

a. If a vending machine will only accept coins weighing between 5.428 g and 5.82 g, what % of legal quarters will be rejected?

b. If the quarters having weights in the lowest 0.5% and highest 0.5% weight range are to be rejected, what are the two cutoff weights?

Come on! You can't miss these.

(5.482-5.67)/0.07 = Zbottom
(5.82-5.67)/0.07 = Ztop

Part B is just the reverse.

 

[Angel626]

i got -2.7142857129 and 2.14285714286

-2.7142857129 corresponds with a percentage of .33%?

2.14285714286 corresponds with a percentage of 1.61%?

 

[tkhunny]

How can the same z-score produce different results? Isn't the Normal Distribution symmetric?

 

[Angel626]

I look at the Positive Z score table?