What is the value of a 6 15 -- = ------- 22 a
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Answer:
And we are 95% confident that the true difference means are between
Step-by-step explanation:
We know the following info:
sample mean for group 1
sample mean for group 2
sample standard deviation for group 1
sample standard deviation for group 2
sample size group 1
sample size group 2
We want to find a confidence interval for the difference of means and the correct formula to do this is:
Now we just need to find the critical value. The confidence level is 0.95 then the significance is and
. The degrees of freedom are given by:
The critical value for this case would be :
And replacing into the confidence interval formula we got:
And we are 95% confident that the true difference means are between
In every case, you're finding the surface area of a rectangular prism. That area is the sum of the areas of the 6 rectangular faces. Since opposite faces have the same area, the formula can be written
... S = 2(LW +WH +HL)
The number of multiplications can be reduced if you rearrange the formula to
... S = 2(LW +H(L +W))
where L, W, and H are the length, width, and height of the prism. (It does not matter which dimension gets what name, as long as you use the same number for the same variable in the formula.)
When you're evaluating this formula over and over for diffferent sets of numbers, it is convenient to let a calculator or spreadsheet program do it for you.
1. S = 2((5 cm)(5 cm) +(5 cm)(5 cm +5 cm)) = 2(25 cm² +(5 cm)(10 cm))
... = 2(25 cm² + 50 cm²) = 150 cm²
2. S = 2(12·6 + 2(12+6)) mm² = 2(72 +36) mm² = 216 mm²
3. S = 2(11·6 + 4(11 +6)) ft² = 2·134 ft² = 264 ft²
4. S = 2(10·4 +3(10 +4)) in² = 164 in²
