Question

Todd Holland from NY grows pumpkins. He studied his past records carefully and concluded that his biggest pumpkins are distributed according to a normal distribution with mean 950 lbs and standard deviation 50 lbs. (a) What is the probability for Todd to get his biggest pumpkin weighing more than 1000 lbs

Answer 1

Answer:

$P(X>1000)$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

If we apply this formula to our probability we got this:

$P(X>1000)=P(\frac{X-\mu}{\sigma}>\frac{1000-\mu}{\sigma})=P(Z>\frac{1000-950}{50})=P(z>1)$

And we can find this probability using the complement rule and the normal standard table and we got:

$P(z>1)=1-P(z$

Step-by-step explanation:

Previous concepts

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".  

Solution problem

Let X the random variable that represent the variable of interest of a population, and for this case we know the distribution for X is given by:

$X \sim N(950,50)$  

Where $\mu=950$ and $\sigma=50$

We are interested on this probability

$P(X>1000)$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

If we apply this formula to our probability we got this:

$P(X>1000)=P(\frac{X-\mu}{\sigma}>\frac{1000-\mu}{\sigma})=P(Z>\frac{1000-950}{50})=P(z>1)$

And we can find this probability using the complement rule and the normal standard table and we got:

$P(z>1)=1-P(z$