# Normal Probability Distribution

8 Questions

QUESTION 1 of 8

I am in your Sta2021 class.I was doing the assignment from StatsProfessor on 5.2, where it said "Now you try it" , I am have issues with number 2. The question is P(1400 < X < 1700) , When I work it out, I get .3539 but on your answer sheet, it said the answer is .3529, I want to understand what I am doing wrong.

QUESTION 2 of 8

Professor,

I need help on problem 12 on the homework on section 5.1

I am not sure if I am looking for the shade side or all together?

Could you please clarify, all the set of the problems i did well bu stuck on this one.

Thanks

QUESTION 3 of 8

Hi Professor,
I am having trouble on how you found the answer for 13B in homework 6.2
I got the answer O, but how did you get 0.0001
Thank you

QUESTION 4 of 8

Hi Professor,

Question on Homework Problem number 14 under section 5.3. When I solve for the z-score I get -3.04 but then the I get stuck because I am not getting the right answer.

Among women aged 15 to 44, average age at first sexual intercourse was 17.3 years. Their male
counterparts lost their virginity at 17.0 years on average both groups had a standard deviation of
2.17 years. What is the probability that a randomly chosen group of 36 females lost their virginity
at an age under 16.2 years old?

Thank you.

QUESTION 5 of 8

Hi Professor,

I had another question about Now You Try It! For Section 6.2. If your looking for the average weight between 40 and 41 wouldn't you add the areas 0.4911 and 0.4370, instead of subtracting? Also, can you go through the problem.

Thank you,
Natalie

Question:
It is recommended that backpacks weigh less than 1/4
th of your body weight. The average backpack with four textbooks and school supplies weighs 38.2 pounds with a standard deviation 7.1 pounds. If a randomly selected group of 36 backpacks is
weighed what is the probability that the average weight for the packs is between 40
and 41 pounds?

QUESTION 6 of 8

Hi professor, I have encountered a couple of problems in section 5.2 hw when they ask to find the probability between numbers. Number 20, asks for the probability for a randomly selected dieter on the plan he is on to loose between 5 and 10 pounds. So when i draw it, i shade in what is between 5-10, but then there is 2 empty spaces everything below 5 and after 10, so I am not sure how i am supposed to calculate after i get the z scores?

Then 25) its finding the probability between 145 and 146, so I find the z score for 145, which is 0.4207, and 146 is 0.2673, now what calculation do i have to do because i am stuck in the same position as #20, since is it a shaded part in the same side, i do not know what to do, maybe i am shading wrong?

Then for 29) I get that z score of 0.2486 and 0.4032, and i was adding them, but it is the wrong answer. I shaded between 110 and 120 on the right side?

31) I found the z scores as well 0.4192 and 0.3413, but i do not know what to do with the numbers, since i shaded in between 155 and 165.