With a 95 percent confidence interval, you have a 5 percent chance of being wrong. With a 90 percent confidence interval, you have a 10 percent chance of being wrong. A 99 percent confidence interval would be wider than a 95 percent confidence interval (for example, plus or minus 4.5 percent instead of 3.5 percent).
Q. What is a good standard error value?
Thus 68% of all sample means will be within one standard error of the population mean (and 95% within two standard errors). The smaller the standard error, the less the spread and the more likely it is that any sample mean is close to the population mean. A small standard error is thus a Good Thing.
Table of Contents
- Q. What is a good standard error value?
- Q. What is the relationship between sample size and the standard error of the mean?
- Q. Is a 95 confidence interval wider than a 90?
- Q. What is the critical value for a 95% confidence interval?
- Q. What is the critical value of 99%?
- Q. What is the critical value for a 80 confidence interval?
- Q. What is the T critical value for a 99 confidence interval?
- Q. What is the T score for a 90 confidence interval?
- Q. How do you find the critical value?
Q. What is the relationship between sample size and the standard error of the mean?
The standard error is also inversely proportional to the sample size; the larger the sample size, the smaller the standard error because the statistic will approach the actual value.
Q. Is a 95 confidence interval wider than a 90?
The 95% confidence interval will be wider than the 90% interval, which in turn will be wider than the 80% interval. For example, compare Figure 4, which shows the expected value of the 80% confidence interval, with Figure 3 which is based on the 95% confidence interval.
Q. What is the critical value for a 95% confidence interval?
1.96
Q. What is the critical value of 99%?
Confidence (1–α) g 100% | Significance α | Critical Value Zα/2 |
---|---|---|
90% | 0.10 | 1.645 |
95% | 0.05 | 1.960 |
98% | 0.02 | 2.326 |
99% | 0.01 | 2.576 |
Q. What is the critical value for a 80 confidence interval?
Checking Out Statistical Confidence Interval Critical Values
Confidence Level | z*– value |
---|---|
80% | 1.28 |
85% | 1.44 |
90% | 1.64 |
95% | 1.96 |
Q. What is the T critical value for a 99 confidence interval?
Student’s T Critical Values
Conf. Level | 50% | 99% |
---|---|---|
One Tail | 0.250 | 0.005 |
80 | 0.678 | 2.639 |
90 | 0.677 | 2.632 |
100 | 0.677 | 2.626 |
Q. What is the T score for a 90 confidence interval?
For example, if you want a t*-value for a 90% confidence interval when you have 9 degrees of freedom, go to the bottom of the table, find the column for 90%, and intersect it with the row for df = 9. This gives you a t*–value of 1.833 (rounded).
Q. How do you find the critical value?
To find the critical value, follow these steps.
- Compute alpha (α): α = 1 – (confidence level / 100)
- Find the critical probability (p*): p* = 1 – α/2.
- To express the critical value as a z-score, find the z-score having a cumulative probability equal to the critical probability (p*).