The lifetimes of a certain type of light bulbs follow a normal distribution. if approximately 2.5% of the bulbs have lives exceeding 445 hours, and approximately 16% have lives exceeding 393 hours, what are the mean and standard deviation of the lifetimes of this particular type of light bulbs? round your answer to the nearest integer. mean = hours tries 0/5 standard deviation = hours

Mean = 339 hours

Standard deviation = 54 hours

Step-by-step explanation:

We are given that approximately 2.5% of the bulbs have lives exceeding 445 hours

So,P(x>445) = 0.025

P(x<445) =1- 0.025 =0.975

 z value for 0.975 is 1.96

Formula :

So,

--A

Now we are given that  approximately 16% have lives exceeding 393 hours,

So,P(x>393) = 0.16

P(x<393) =1- 0.16 =0.84

 z value for 0.84 is 1

Formula :

So,

---B

Solve A and B

Substitute the value of from B in A

Substitute the value in B

So, mean = 339 hours

Standard deviation = 54 hours

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step-by-step explanation:

5.7622

step-by-step explanation:

the ten thousandths place is the 2. you round it up if, that number in whatever place is 5 or higher.