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11
votes
2
answers
7k
views
Calculate the standard error of the difference between two independent proportions
interval (95%) =
Margin of error = Square root [p(1-p)/n] * 1.96 //
n = sample size, 1.96 is 95% confidence interval
Margin error1 = sqrt(0.194304/500) * 1.96 = 0.01971314282 * … 1.96 = 0.038637759
Margin error2 = sqrt(0.218620357/700) ] * 1.96 = 0.01767240787 *
1.96 = 0.034637919
P + margin of error = Upper confidence interval
p1 = 0.264+0.038637759 …
1
vote
How many test executions are required (and how many must pass) to say my software works 90% ...
You need to determine a margin of error. The margin of error tells you, roughly, the likely amount of sampling error from a sample of observations. … Footnotes
The actual margin of error for a binomial random variable is
$$ z_{1-\alpha/2} \times \sqrt{\dfrac{p(1-p)}{N}} $$
and is equal to the radius of the Wald confidence interval for the binomial …
2
votes
2
answers
2k
views
Confidence interval vs. prediction interval misunderstanding
I started realizing that expecting a 90% confidence interval to contain about 90% of the sample is a popular misunderstanding because the confidence interval is a statement about the population statistic … I saw something about using the RMSE instead of standard deviation in a confidence interval and adding the 90% t-value and RMSE based margin of error to the mean. …
68
votes
6
answers
10k
views
Are all values within a 95% confidence interval equally likely?
This blogpost, titled Within the Margin of Error, states:
What I have in mind is misunderstanding about “margin of error” that treats all points within the confidence interval as equally likely, as … The thing that talk about “margin of error” misses is that possibilities that are close to the point estimate are much more likely than possibilities that are at the edge of the margin". …
0
votes
0
answers
16
views
Group Sample size
I assume a standard normal distribution will fit I initially set a margin of error at 5%, with a 90% confidence level and assumed a 50% standard deviation, which resulted in a sample size of around 270 …
0
votes
0
answers
37
views
Why are confidence intervals valid? [duplicate]
By definition, our confidence level will represent the percentage of total samples from our sample distribution that are within the margin of error of the true population statistic. … In these cases, we use the standard error to approximate the standard deviation: $\frac{s_x}{\sqrt(n)}$. …
7
votes
Correlation for Small Dataset?
In line with the answer @Glen_b in the worst case (true correlation is zero) you need 300-400 observations to well-estimate $r$, e.g., to within a margin of error of 0.1 with 0.95 compatibility. … That is when the margin of error gets closer to 0.1, for example. …
0
votes
0
answers
63
views
How to express the uncertainty in the OR of a right-tailed Fisher's exact test?
Many OR (odds ratio) visualizations show 95% confidence intervals expressing uncertainty like on the left panel in figure below. … So how can appropriate confidence intervals or error margins be calculated, or uncertainty properly be expressed in visualization respectively? …
0
votes
Error Propagation of standard deviation?
Your number of statistical degrees of freedom should be 1 (since you only have two samples), and you'll have to choose a suitable two-sided confidence interval. … These two values allow you to retrieve the correction factor in the table (e. g., 6.314 for a 95% confidence interval) and to calculate the corrected error margins. …
0
votes
0
answers
8
views
Can you build up statistical validity with multiple month's worth of the same survey questions?
The idea being that 1500 surveys with a 12% response rate is much healthier for determining a positive confidence level and margin of error compared to a 12% response rate for 750. …
0
votes
1
answer
33
views
Sample size for survey
My survey should be done by enough people so each one of these two groups of people are significantly represented, with a confidence level of 95% and a margin of error of 5%, although these values can … I know that the more margin of error I have, the smaller the sample. Up to which value could it be justified? …
2
votes
Why do physicists use sigma while biologists use p values/posterior probabilities?
From these, she computes the temperature coefficient with three significant digits and a relative confidence interval of about one percent. … Now, if you are used to thinking of error margins, σ is only a small extension of this, whereas p values and similar are a completely new world.
Physics experiments can easily provide a lot of data. …
3
votes
Accepted
How many observations required to meaningful correlation?
You'll see that n=400 is required to estimate the correlation coefficient to within a margin of error of +/- 0.1 with 0.95 confidence, if you know nothing about the true correlation. …
0
votes
1
answer
33
views
binomial data, margin of error, standard error of a sample
But the margin of error is 3%).
Trying to understand how this "margin of error" is calculated I searched the internet and came across this article. … Using a
level of confidence of 95%, they can determine that the margin of
error is 2%. Anything between 65% and 69% (67% +/- 2) accurately
describes the entire customer database. …
2
votes
Accepted
binomial data, margin of error, standard error of a sample
The margin of error for some level of confidence (say 95%) is the critical value, multiplied by the standard error. … Multiplying these two together gives $0.017=1.7\%$, which is approximately the 2% margin of error stated in the article. …