Tagged Questions

4
votes
3answers
118 views

Problem with p-values from A/B testing

I'm pretty confused right now and the more I look at it, the more confused I get. Overthinking! I'm doing some A/B tests for my website. I'm using the significance calculator that's in this article: ...
0
votes
1answer
43 views

Conservative confidence interval

One month before the election, a poll of a large number of randomly selected voters showed 65% planning to vote for a certain candidate. The newspaper article reported a 90% conservative margin of ...
0
votes
0answers
22 views

Difference between chi statistical methods (pearson/likelyhood/linear-by-linear)

Can someone briefly explain the differences between these three tests? When would you use one over the other? Which tests are associated with a test of independence, homogeneity, or goodness-of-fit? ...
1
vote
1answer
39 views

Chi squared test of homogeneity

Suppose you want to test the null hypothesis: H0: p1 = 0.65, p2 = 0.27, p3 = 0.01, p4 = 0.05, p5 = 0.02 to determine whether a population's distribution matches the proposed proportions. You ...
2
votes
3answers
67 views

Population with known distribution (not normal) versus small sample

I have a complete population consisting of 6587 individuals (genes) and for each individual I have a distance value. These distance values are not normally distributed. I'm interested in determining ...
0
votes
1answer
235 views

Finding the z score and p-value of a binomial distribution

Emily is a big fan of lady gaga, and 20% of the songs on her ipod are lady gaga songs. Suppose Emily has her ipod on shuffle and repeat mode, which can be assumed to mean that each song to be played ...
0
votes
2answers
109 views

Why doesn't this represent a normal approximation to the binomial?

Suppose the registrar's office at a college reports 58% of the students live on campus. An intern working in the administration building is unaware of this 58% parameter value. He designs a study in ...
1
vote
2answers
51 views

I want to compare two groups of coin tosses with different number of tosses

I have a list of results of two different groups of coin tosses generated by http://www.wolframalpha.com/input/?i=10+coin+tosses. But the number of tosses is different: There are 10 in one group and ...
0
votes
1answer
210 views

P values and t statistics?

I performed an experiment using two different methods on same object, the results of the experiments were Method 1 70,72,70,75 and 77% Method 2 80,81,67,75 and 82% On basis on average I claimed ...
1
vote
1answer
89 views

Distribution of $R^2$ for pairs of random variables

if I have two uniform random variables $X$ and $Y$, and I sample $N$ values for each, what's the probability of getting an $r$ Pearson's correlation coefficient (or Spearman correlation) between them ...
1
vote
1answer
216 views

Frequentist properties of p-values in relation to type I error

This question is related to frequentist properties of p-values and their relation to type I error and why the results from an online simulation differ from what I would have expected. Assume that I ...
8
votes
3answers
2k views

Comparing and contrasting, p-values, significance levels and type I error

I was wondering if anybody could give a concise rundown as to the definitions and uses of p-values, significance level and type I error. I understand that p-values are defined as "the probability of ...
10
votes
5answers
464 views

Confidence interval and probability - where is the error in this statement?

If someone makes a statement like below: "Overall, nonsmokers exposed to environmental smoke had a relative risk of coronary heart disease of 1.25 (95 percent confidence interval, 1.17 to ...
2
votes
3answers
279 views

Probability of head in coin toss is not exactly 1/2!

I kinda heard that usual coins are not exactly fair. The experiment done way ago and one done relative recently could reject the null hypothesis of p=1/2 after maybe hundreds of thousands of coin ...
1
vote
1answer
630 views

Compare the difference of two probabilities or a ratio of probabilities?

In an experiment with continuous-value random variable, e.g. measuring length of cucumbers. I would like to compare the probability of getting a particular length range in two different conditions. ...
0
votes
0answers
43 views

Effect of uncertainty in a parameter of a probability model on decisions — follow-up

I wrote this question which was previously answered I am exposing several experimental organisms to a toxin in the food. If the dosage is high enough, they will die. I am examining the number ...
6
votes
2answers
2k views

How to choose significance level for a large data set?

I am working with a data set having N around 200,000. In regressions, I am seeing very small significance values << 0.001 associated with very small effect sizes, e.g. r=0.028. What I'd like to ...
3
votes
3answers
95 views

Effect of uncertainty in a parameter of a probability model on decisions

I am exposing several experimental organisms to a toxin in the food. If the dosage is high enough, they will die. I am examining the number that are dead after a day. For practical reasons, the ...
7
votes
2answers
261 views

Does an exact test always yield a higher P value then an approximated test?

I ran a simulation on that for mcnemar test, and the answer seemed to be yes. I was wondering if this can always be said to be the case that the exact P value is higher (or not smaller) then the p ...
2
votes
0answers
225 views

Distribution of the size of overlap between two random samples with duplicates?

Similar to this question, I want to know if the overlap between two samples is significant. However, my items are not unique; I have c distinct colors of items, there are mi items of color i (1 < ...
2
votes
0answers
63 views

Determining the significance of a set ordering

First some preamble: Let A be a set of unordered elements, and let A' and A'' be subsets of A, where |A'| = |A''| = k. It’s given that as k approaches |A|, for every x in A' there is an increased ...