# Statistics Help

- 0Nov 30, '10 by KhansenA person’s blood glucose level and diabetes are closely related. Let x be a

random variable measured in milligrams of glucose per deciliter (1/10 of a liter)

of blood. After a 12-hour fast, the random variable x will have a distribution

that is approximately normal with mean μ=85 and standard deviation σ=25.

After 50 years of age, both the mean and the standard deviation tend to increase.

What is the probability that, for an adult (under 50 years old) after 12-hour

fast,

(a) x is more than 60?

(b) x is less than 110?

(c) x is between 60 and 110?

(d) x is greater than 140 (borderline diabetes starts at 140)? - 1Nov 30, '10 by shaashere is how i approach it:

1) the purpose of standard deviation is to be added to or subtracted (±) from the mean value to give you__a range of values__

2) so, the mathematical application is:

range = 85 ± 25

3) determining the range:

upper limit (addition) = 85 + 25 = 110 mg/dl

lower limit (subtraction) = 85 - 25 = 60 mg/dl

so, the range of her blood glucose level is somewhere between 60 mg/dl and 110 mg/dl.

now, normal distribution means a regular bell-curve, which means this calculation satisfies the range of values as well.

you should be able to calculate the rest by using the eq__n__shown above for each section of the bell-curve.

here also is a helpful site: http://stattrek.com/lesson2/normal.aspxLast edit by shaas on Nov 30, '10TnRN43 likes this. - 0Nov 30, '10 by moonchild86What area of stats are you working on right now? Do you guys use tables and z-scores at all? This is how we would approach this problem.. (I think.. lol)

1) First list what is given: (will go with "A" for right now)

μ=85, σ=25, X=60

2) List what you're looking for: Find the probability that X >60

3) Find Z: z= x-μ/σ

Z= 60-85/25= -1

4) Convert Z to a percent (Using using statistic table A or B- can't remember exactly)

-1 = 34.13%

5) Convert percent to a probability. (Simply move the decimal)

P= .3413

6) Fine probability: To find a probability at or above- subtract from .5 to find a probability at or below we add to .5

.5- .3413 = .1587 (for "b" you'll add the probability to .5)

6) List answer:

There is a .1587 probably that X is above 60..

I might be totally off base.. this is based on our chapter in statistics and parameters.Last edit by moonchild86 on Nov 30, '10