I need help with these objective questions

1.Calcium and Vitamin D are important for healthy bones. Researchers would like to know the optimal levels for a supplement pill. Calcium will be given at two doses (500 mg/day and 700 mg/day). and Vitamin D will be given at two doses (600 IU/day and 800 IU/clay). Volunteers will be randomly assigned one of the treatments. Bone density tests will be done on all of the volunteers before the study and then repeated again six months later to see if there has been an increase in bone density. Effects of the treatments are expected to differ depending on a subject's age. so the experiment is conducted separately for children. adults and seniors.

This is an example of: -a randomized block design with tree factors and three blocks. -a completely randomized design with three factors. -a completely randomized design with two factors. a randomized block design with four factors and two blocks

-a randomized block design with two factors and three blocks.

2. How many of the following statements regarding experimental design are true?

(I) A control group is not always necessary to achieve control in an experiment, as long as we are comparing at least two treatments. (II) In a double blind experiment, the person administering the treatments does not know what treatment a subject is receiving. (III) If an experiment is designed properly, we should be able to conclude that any observed differences in responses are caused by the different treatments. (IV) In a matched pairs_lexperiment, only two treatments can be compared.

3. A variable X has a uniform distribution on the interval from -12 to 12. What proportion of values of X are greater than 7?

0.4167 ,0.2917 , 0.5833, 0.2083 0 0.4475

4. The variable Zhas_ a standard normal distribution. if P(-0.62 < Z< c) = 0.6915 then the value c is equal to

-1.87

-1.42

-1.74

-1.55

-1.63

5. The time (in seconds) it that takes mice to run through a cardboard maze follows a normal distribution with mean 135 and standard deviation 25. Only 29% of mice will have times greater than: 121.25 seconds, 142.25 seconds, 152.75 seconds , 148.75 seconds, 117.25 seconds

6. Monthly electric bills for houses in a big city follow a normal distribution with mean $120 and standard deviation $27. What proportion of houses have a monthly electric bill between $80 and $170? 0.8984, 0.8173, 0.8708, 0.8362, 0.8547