The 68-95-99.7 rule tells us 68% of the probability is between -1 standard deviation and +1 standard deviation from the mean. So we expect 75% corresponds to slightly more than 1 standard deviation.
Usually the unit normal tables don't report the area between -σ and σ but instead a cumulative probability, the area between -∞ and σ. 75% corresponds to 37.5% in each half so a cumulative probability of 50%+37.5%=87.5%. We look that up in the normal table and get σ=1.15.
So we expect 75% of normally distributed data to fall within μ-1.15σ and μ+1.15σ
That's 288.6 - 1.15(21.2) to 288.6 + 1.15(21.2)
Answer: 264.22 to 312.98
Answer:
12 is the answer
Step-by-step explanation:
It’s B because
Explanation: Since they've given use the area of the triangle, we can use the area formula to find the base of the triangle. The formula to find the area of a triangle is: a=12hb.
A light bulb manufacturer guarantees that the mean life of a certain type of light bulb is at least 720 hours.a random sample of 51 light bulbs as a mean of 712.8 hours with a population standard deviation of 62 hours at and a equals 0.05 can you support the company's claim using the test statistics?
These are just multiplications. For percents we have to move the decimal point two places. I assume calculators are OK.
2.
19.6% of 244 = .196(244) = 47.824
3.
20% of 75 = .2 (75) = 75/5 = 15
Didn't need a calculator for that one.
