Answer:
standard error = 1.63
Step-by-step explanation:
To calculate the standard error we need to know the standard deviation (σ) and the sample size (n) (see the attached formula).
To obtain the standard deviation we use the given sample variance of 77.4 years:
σ²= variance
Therefore:
σ = √77.4 = 8.8
Now we can calcuate the estimated standard error:
standard error = σ /√n = 8.8/√29 = 1.63
The standard error gives us an estimation about how far the mean of the sample is from the mean of the entire population, and in this case is 1.63.
<span>n Billy's class, 75% of his classmates had brown hair. 18 of his classmates had brown hair. What's the total number of students in his class?</span>
Let n represent the number.
-13×(n -60) = n +(-59)
-13n +780 = n -59
839 = 14n
839/14 = n = 59 13/14
The number is 59 13/14.
_____
Check
The difference between the number and 60 is
59 13/14 -60 = -1/14
-13 times that value is
-13*(-1/14) = 13/14
Compare that to the number plus -59
59 13/14 -59 = 13/14 . . . . . the same value, as required.
Answer:
15..
Step-by-step explanation:
4, 10, 14, 18, 22, 22
Mean = (4 + 10 + 14 + 18 + 22 + 22)/6
= 90/6
= 15.
Number to be added, 'y'
For the mean to be the same
(90 + y) / 7 = 15
90 + y = 15 × 7
90 + y = 105
y = 105 - 90
= 15
