The average 7

The average lifespan for cricket is 90 days, with a standard deviation of 13 days. If we assume that the lifespan of cricket is normally distributed,
a. What is the probability a randomly selected cricket has a lifespan of fewer than 75 days?
b. What is the probability a randomly selected cricket will have a lifespan between 80 and 120 days?
c. What is the probability a randomly selected cricket will have a lifespan of more than 100 days?

Correct answer:

p₁ =  0.1243
p₂ =  0.7686
p₃ =  0.2209

Step-by-step explanation:

$$\begin{gathered} m=90 \\ \sigma =13 \\ {p}_1=N(m,\sigma ,x<75) \\ {p}_1=0.1243 \end{gathered}$$

Use the normal distribution table.

$$\begin{gathered} p_2=N(m,\sigma ,80<x<120) \\ {p}_2=0.7686 \end{gathered}$$

Use the normal distribution table.

$$\begin{gathered} p_2=N(m,\sigma ,x>100) \\ {p}_3=0.2209 \end{gathered}$$

Use the normal distribution table.

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