"If you used the normal approximation to estimate how many of these measurements were in the range 400 to 406 micrograms, would your answer be too low, too high, or about right?

Step-by-step explanation:

Prob(400<Xbar<406)=Prob(-13.338<t<2.77)=0.99

By normal approximation the no of measurements in the range of 400 to 406 is =n× 0.99=100 × 0.99=99

Which is slightly high compared to actual data.however we must consider that these approximation have an error component.so it is not accurate always.

452,489 to the nearest thousand is 452,000

b. 1.25 hr

step-by-step explanation:

if you have a constant speed of 60 mph, then you have a ratio between 60 mi. to 1 hr. dividing both sides by 60 we get the ratio

1 mi. to

then mult. both sides by 75 we get the ratio

75 mi. to

simplifying we get

75 mi. to

or 1.25 hr.