Economic Statistic Exam Case Solution
The probability is 0.9649 or 96.49 percent that the number of people that you would have needed to poll in order to be 99% sure that the `yes' side will win the referendum (in other words, so that there is only a 1% chance that `no' will win).
- The variance of the sample proportion is
V = N * P * Q
V = 500 * 54 % * 46 %
V = 124.2
- Standard Deviation is
STDEV = V ^ (1/2)
STDEV = 124.2 ^ (1/2)
STDEV = 11.145
Question 3
Interruptions (X) |
|
X - Mean | (x - Mean)2 | |
0 | 0.32 | 0.177143 | 0.03138 | |
1 | 0.35 | 0.207143 | 0.042908 | |
2 | 0.18 | 0.037143 | 0.00138 | |
3 | 0.08 | -0.06286 | 0.003951 | |
4 | 0.04 | -0.10286 | 0.01058 | |
5 | 0.02 | -0.12286 | 0.015094 | |
6 | 0.01 | -0.13286 | 0.017651 |
- The mean or expected number of interruptions per day is
(0.32 + 0.35 + 0.18 + 0.08 + 0.04 + 0.02 + 0.01) / 7 = 0.1429
- The standard deviation of expected number of interruptions per day is
((Sum of (x – Mean)2) / (total number of interruptions – 1)) (1/2) = 0.01025
- P (X ≥ 18)
P(X≥ 18) = P (Z ≥ ((18 – 14.29) / 1.025))
P(X≥ 18) = P (Z ≥ 3.62)
P(X≥ 18) = 1 – 0.9998
P(X≥ 18) = 0.0002
The probability is 0.0002 or 0.02 percent that the value of X will be 18 or greater than 18.
- P(X≥ 17)
P(X≥ 17) = P (Z ≥ ((17 – 14.29) / 1.025))
P(X≥ 17) = P (Z ≥ 2.64)
P(X≥ 17) = 1 – 0.9959
P(X≥ 17) = 0.0041
The probability is 0.0041 or 0.41 percent that the value of X will be 17 or greater than 17.
Question 4
N = 200
Mean = 5
Variance = 10 ^ 2
Standard Deviation = 10
- P (X ≤ 99)
P(X≤99) = P (Z ≤((99 – 5) / 10))
P(X≤99) = P (Z ≤9.4)
P(X≤99) = 0.9998
- P (X ≤ 99)
P(X≤99) = P (Z ≤((99 – 5) / 10))
P(X≤99) = P (Z ≤9.4)
P(X≤99) = 0.9998
- The probability is 0.9998 or 99.98 percent that the confidence interval containing the true mean with a probability of at least 0.99, using the weak law of large numbers (WLLN).
- The Chebyshev's Theorem is a fact that applies to all possible data sets. It describes the minimum proportion of the measurements that lie must within one, two, or more standard deviations of the mean.
- For each CLT and WLLN, the rate at which confidence bands become narrower as sample size increases is
CLT | WLLN | Rate |
200 | 200 | 100.00% |
199 | 199 | 99.50% |
198 | 198 | 99.00% |
197 | 197 | 98.50% |
196 | 196 | 98.00% |
195 | 195 | 97.50% |
194 | 194 | 97.00% |
193 | 193 | 96.50% |
192 | 192 | 96.00% |
191 | 191 | 95.50% |
190 | 190 | 95.00% |
189 | 189 | 94.50% |
188 | 188 | 94.00% |
187 | 187 | 93.50% |
3 | 3 | 1.50% |
2 | 2 | 1.00% |
1 | 1 | 0.50% |
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