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Chapter 2: Q 87. (page 143)

The weights of laboratory cockroaches can be modeled with a Normal distribution having mean 80 grams and standard deviation 2 grams. The following figure is the Normal curve for this distribution of weights.

Point C on this Normal curve corresponds to

a.84grams.b.82grams.c.78grams.d.76grams.e.74grams.

Short Answer

Expert verified

The correct option is (b) 82grams

Step by step solution

01

Given information

Population mean (渭)=80

Population standard deviation (s)=2

02

Calculation

Consider X to be a random variable that represents cockroach weight in grams.

The percentage of cockroaches weighing between 76 and 84 grams is computed as follows:

P(76<X<84)=P(76鈭�渭蟽<Z<84鈭�渭蟽)=P(76-802<Z<84-802)=P(鈭�2<Z<2)=0.95

Thus, the required proportion is approximately 95%

Hence, the correct option is(b)

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