I have an expression
floating around in my head; let's see if it makes sense.
The variance of binary valued random variable b that comes up 1 with probability p (so has mean p) is
That's for an individual sample. For the observed average we divide by n, and for the standard deviation we take the square root:
Plugging in the numbers,
One standard deviation of the average is almost 2% so a 27% outcome was 3/1.9 = 1.6 standard deviations from the mean, corresponding to a two sided probability of a bit bigger than 10% of happening by chance.
So this is borderline suspect; most surveys will include a two sigma margin of error, say plus or minus 4 percent here, and the results were within those bounds.
Answer:
12)
(9y +7)=(2y +98)( Because vertically opposite angle is always equal)
9y - 2y = 98-7
9y - 2y = 98-7
7y= 91
y =13
<em>ther</em><em>fore</em><em> </em><em>y</em><em> </em><em>=</em><em> </em><em>1</em><em>3</em>
<em>(</em><em>9</em><em>y</em><em> </em><em>+</em><em> </em><em>7</em><em>)</em>
9*13+7
117+7
124
(2y +98)
2*13+98
26+98
124
-6 you subtract and keep the sign of the greater number
<span>The <u>correct answer</u> is:
A) 60% ± 18%.
Explanation:
In a confidence interval, the margin of error is given by z*(</span>σ/√n<span>), where </span>σ<span> is the standard deviation and n is the sample size.
First we <u>find the value of z</u>:
We want a 95% confidence level; 95% = 95/100 = 0.95.
To find the z-score, we first subtract this from 1:
1-0.95 = 0.05.
Divide by 2:
0.05/2 = 0.025.
Subtract from 1 again:
1-0.025 = 0.975.
Using a z-table, we find this value in the middle of the table. The z-score that is associated with this value is 1.96.
Back to our formula for margin of error, we have 1.96(</span>σ<span>/</span>√n<span>). The larger n, the sample size, is, the larger its square root is. When we divide by a larger number, our answer is smaller; this gives us a smaller margin of error.
This means that if we had a small sample size, we would divide by a smaller number, making our margin of error larger. The largest margin of error we have in this question is 18%, so this is our correct answer.</span>
