Data consistent with summary quantities in the article "Effects of Fast-Food Consumption on Energy Intake and Diet Quality Among
1 answer:
Answer:
a) X[bar]₁= 1839.20 cal
b) X[bar]₂= 1779.07 cal
c) S₁= 386.35 cal
Step-by-step explanation:
Hello!
You have two independent samples,
Sample 1: n₁= 15 children that did not eat fast food.
Sample 2: n₂= 15 children that ate fast food.
The study variables are:
X₁: Calorie consumption of a kid that does not eat fast food in one day.
X₂: Calorie consumprion of a kid that eats fast food in one day.
a)
The point estimate of the population mean is the sample mean
X[bar]₁= (∑X₁/n₁) = (27588/15)= 1839.20 cal
b)
X[bar]₂= (∑X₂/n₂)= (26686/15)= 1779.07 cal
c)
To calculate the sample standard deiation, you have to calculate the sample variance first:
S₁²= [∑X₁² - (( ∑X₁)²/n₁)]=
= 149263.4571 cal²
S₁= 386.35 cal
I hope it helps!
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Your calculator's cubic regression function can tell you the equation is
... f(x) = 2x³ + 5x² -12x = x(x +4)(2x-3)
The x-intercepts are -4, 0, +1.5.
_____
If you want to solve this "by hand", you can first of all recognize that since there is an x-intercept at 0, the cubic will only have three coefficients. That is, you can write the equation as
... f(x) = ax³ + bx² + cx
Substituting the given points (except (0, 0)) gives three linear equations in a, b, c.
... -a +b -c = 15 . . . . . for x=-1
... a + b + c = -5 . . . . for x=1
... 8a +4b +2c = 12 . . for x=2
adding the first two equations gives 2b=10, or b=5. Now, you can reduce the system to
... a + c = -10
... 4a +c = -4
Subtracting the first of these equations from the second gives 3a=6, or a=2. That tells you c=-12 (from a+c=10).
Then your equation is
... f(x) = x(2x² +5x -12)
Factoring by any of the usual techniques, or graphing, or using the quadratic formula will tell you the zeros (x-intercepts) are as above.
_____
Since the input values are sequential, you can also develop the function from differences of the output values. Those are 15, 0, -5, 12. First differences are -15, -5, +17. Second differences are +10, +22. The third difference is 12. Using the first of these differences in appropriate places in the interpolating polynomial formula, we have
... f(x) = 15 + (x+1)(-15 + (x)/2·(10 + (x-1)/3·(12))) = 2x³ +5x² -12x . . . . as above
Answer:
0.3745
Step-by-step explanation:
Data
mean (): 80
standard deviation (): 4
Normal distribution table is in figure attached .
Z = (85 - 80)/4 = 1.25
Area below curve = 0.3944
Z = (82 - 80)/4 = 0.5
Area below curve = 0.0199
Proportion of exam scores between 82 and 85?
0.3944 - 0.0199 = 0.3745
