Question

The seasonal output of a new experimental strain of pepper plants was carefully weighed. The mean weight per plant is 15.0 pounds, and the standard deviation of the normally distributed weights is 1.75 pounds. Of the 200 plants in the experiment, how many produced peppers weighing between 13 and 16 pounds

Answer 1

Answer:

There are 118 plants that weight between 13 and 16 pounds

Step-by-step explanation:

For any normal random variable X with mean μ and standard deviation σ : X ~ Normal(μ, σ)  

This can be translated into standard normal units by :  

$Z = \frac{(X - \mu)}{\sigma}$

Let X be the weight of the plant  

X ~ Normal( 15 , 1.75 )  

To find : P( 13 < X < 16 )  

$= P(\frac{( 13 - 15 )}{1.75} < Z < \frac{( 16 - 15 )}{1.75})$

= P( -1.142857 < Z < 0.5714286 )  

= P( Z < 0.5714286 ) - P( Z < -1.142857 )  

= 0.7161454 - 0.1265490  

= 0.5895965  

So, the probability that any one of the plants weights between 13 and 16 pounds is 0.5895965  

Hence, The expected number of plants out of 200 that will weight between 13 and 16 = 0.5895965 × 200

                                            = 117.9193  

Therefore, There are 118 plants that weight between 13 and 16 pounds.