normally distributed lifespan, with a mean of 7.1 years, and standard deviation of 0.5 years. The 4% of items with the shortest lifespan will last less than how many years?

Answer 1

mean 7.1 years average life span

standard deviation = .5 years

4% with the shortest life span have life spans with maximum years?

using the empirical rule, 68-95-99.7

5% is beyond 2 standard deviation from the mean, half on either side

with 2.5% lower than 2 standard deviations which is 7 years

for 4% the life span should be a little higher, such as maybe 7.01?

use z tables or a z calculator to get a more precise number

z=-1.751 for 4%

.5 x 1.751 = 0.08755

7.1 - .08755 = 7.01245 is maximum life span for any of the lowest 4%

they'll last less than 7.01245 years

or about less than 7 years 4 1/2 days

these numbers are so strange, it's likely there's a miscopy or misprint in the problem somewhere

what is the item at the center of this all? a drug? a food item? a president? a marriage? period of peace between major wars? time before the released criminal gets arrested again?