The highest recorded temperature during the month of July for a given year in Death Valley, California has an approximately normal distribution with a mean of 123.8 degrees Fahrenheit and standard deviation of 3.1 deg. F (Weather Source, 2009). What is the probability for a given year that the temperature never exceeds 120 deg. F in a given July in Death Valley? Include leading zero, and state your answer to 3 decimal places.

And we can find this probability using excel or the normal standard tabe and we got:

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 to the problem

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

Where and

We are interested on this probability

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

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

And we can find this probability using excel or the normal standard tabe and we got:

77

step-by-step explanation: