All Questions
32 questions
0
votes
1
answer
65
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Distribution for which one-sample t-test yields inflated type 1 error rates
Type 1 error rates of the one-sample t-test (two-tailed) can be inflated for example for data from the exponential distribution.
However, I am looking for distributions which yield inflated type 1 ...
- 1
4
votes
1
answer
186
views
equal *population* variances in paired t test
I I want to perform a paired t-test to check if there's some effect, I have the distribution of "before" and the distribution of "after" the manipulation. Do I need to assume the ...
- 41
3
votes
1
answer
132
views
Null Hypothesis in Paired t-test
Suppose that I was tasked to find if the mean difference between the current and starting salary of employees is greater than 15,000. How will my null and alternative hypotheses be?
Can it be:
Ho: ...
- 31
0
votes
1
answer
638
views
Hypothesis testing for increase in sales
A company is planning to setup the option for self checkout (SCO) in all of its stores.
As a trial, they are looking to estimate the benefits of SCO in terms of increase in transaction volume by ...
- 53
2
votes
0
answers
150
views
Asymptotic distribution of t-test with two coefficients
I have the following CEF:
$$
y_{i}=\beta_{1} d_{i}+\beta_{2}\left(1-d_{i}\right)+e_{i}
$$
And the following assumptions:
$$
d_{i} \perp\left(y_{i}(0), y_{i}(1)\right)
$$
$$
\mathrm{E}\left[e_{i} \mid ...
2
votes
1
answer
553
views
t- test for non normally distributed sample
I am doing a statistical test (analysis) for the following case:
As part of a product aimed at improving the quality and speed of code writing for developers,
we have implemented a new feature that ...
- 31
0
votes
0
answers
64
views
Understanding the relationship between a 'sampling distribution of a statistic' and a 'population distribution' in the context of a 'hypothesis test'
I would like to confirm that I am understanding the relationship between a sampling distribution of a statistic (an example of a 'statistic' would be a sample mean $\bar{x}$) and a population ...
- 71
3
votes
2
answers
278
views
How to describe in words the logical conclusion of a one-tail t-test?
Lets say we have the following null and alternative hypothesis:
$$H_0: \mu = \mu_0, \; H_A:\mu > \mu_0 $$
Thus, the p-value in this situation represents the probability of obtaining test results ...
- 719
1
vote
1
answer
131
views
Is the t-test to test the difference from 0?
I have a variable x with a mean 1 and sd of 3. So most of the mass is above zero. Let's say I have n=100 observations. A t-test will tell me whether the mean of x E(x) is different from 0 or above 0. ...
- 315
5
votes
1
answer
408
views
Photo attractiveness rating experiment: significance and effect size
I'm a photographer working on a personal project where I experimentally test dating photo advice. I take photos of people under different conditions, changing one variable while keeping others ...
- 51
3
votes
2
answers
1k
views
Hypothesis testing: understanding test statistics and their sampling distribution
I am struggling a bit with the real meaning of the test statistic and their sampling distribution, but I cannot find my answer. So, I am looking for clarifications. Sorry in advance if it seems very ...
- 55
1
vote
0
answers
36
views
Would Performing a T-Test between Nonequal Continuous Distributions Provide Valid Results?
I have two samples, and in performing a Kolmogorov–Smirnov test the sample distributions are shown to be significantly different from each other.
In knowing that the two sample distributions are ...
- 151
1
vote
1
answer
135
views
Hypothesis testing for two-samples
I have some questions regarding the process of choosing the appropriate statistical test. While I was working in my previous company, we were using T-test, Welch or Mann-Whitney for checking the ...
- 111
0
votes
0
answers
63
views
How do I know whether my sample is fair?
I have a time series dataset with 500 million rows, twenty-six columns and 400 thousand unique actors.
It's too much data for me to process all at once, so I want to take a fair sample of my data.
I'...
- 347
1
vote
1
answer
40
views
Is there a situation where you cannot do the T-test for mean inference?
So for mean inference, would there be a situation where you cannot use the T-test? Seems like you can always calculate a t-statistic, so it seems like you can always do the t-test for mean inference.
...
- 3,263
1
vote
0
answers
11
views
How can I compare a sample and population from three percentage groups?
I have data from a national poll whereby three questions were answered with either "Do" "Do not" or "Not sure." I have conducted a random sample poll at my school with the same three questions and ...
0
votes
1
answer
196
views
How to calculate the significance of the difference in average sales in an A/B test
I am doing A/B testing for ad display, where the wording on the ad is different between the two groups.
Metrics gathered:
1) # of people the ad reached
2) # of people who clicked on the ad and were ...
- 41
2
votes
1
answer
1k
views
Confused about the normality assumption of a t-test
I am highly confused about the normality assumption for using a $t$-test. So, as far as I've understood it when you have got $n$ iid normally distributed random variables $X_i$ you can calculate the $...
1
vote
1
answer
73
views
Sampling from the null distribution for a t-test
I am trying to apply the Dietterich 5x2 cv t-test to test whether one statistical model is better than another on a particular data set.
In order to apply this test, one must assume that under the ...
- 3,132
4
votes
3
answers
1k
views
Statistically significant difference between distributions only knowing the mean and std dev?
I have 3 specimens (A, B & C) and 5 sets of observations from A & B but only 4 from C.
Each set of observations has been reported as a mean & a standard deviation. I do not have access to ...
- 213
4
votes
5
answers
2k
views
Why is the concept of the Null hypothesis associated with the student's t distribution?
There are dozens of continuous probability distributions like Gaussian (normal), Variance-gamma, Holtsmark, etc. Yet, the concept of the Null hypothesis is basically associated with Student's t-...
- 107
0
votes
1
answer
114
views
What's the right t-test for comparing the distribution of a response variable across two categories for the same sample?
I have data where every record has an ID, a numeric value (that represents the number of times each ID took a particular action) and a binary state that represents whether they achieved a goal.
...
- 347
1
vote
1
answer
134
views
Testing for difference in means with bimodally distributed data?
I have two bimodal distributions of data with two peaks (one around 0 and the other around 1). I have provided an example of one of the distributions.
Although their means and variances are different,...
- 1,030
2
votes
1
answer
138
views
0
votes
1
answer
883
views
Failing to reject the null hypothesis
I have a very basic doubt but I am new to inference statistics so please pardon me. My question is when we do hypothesis testing for two samples, we estimate the confidence interval and then if the ...
user173461
6
votes
6
answers
2k
views
What is the rationale behind using the t-distribution?
(Probably a very naive question.) According to this tutorial,
Student's t-test deals with the problems associated with inference based on "small" samples: the calculated mean and standard ...
- 207
3
votes
2
answers
777
views
Why my simulation shows T test does not need to have normal distribution assumption on population?
I am trying to learn T statistics and T test using simulation. Why my simulation shows the population distribution does not matter? (In cal_t_stats1, sample was ...
- 37.3k
0
votes
1
answer
70
views
Statistical Significance of three distributions
Within each of the treatment classes below, I have calculated the subgroup as a percentage in each. For example, Treatment A; Subgroup: <29,999 I would divide 769 by the sum of the Person_IDs for ...
4
votes
1
answer
2k
views
Determine if there is a difference between two large vectors of different sizes of non-normal quantiative data in R
I have two vectors that are of unequal sizes. They contain quantitative data that does not form a normal distribution. I would like to see whether or not they are statistically different. Is there a ...
- 169
0
votes
0
answers
140
views
Welch t-test: Exactly when should it be used? [duplicate]
The guidance on this site concerning when to use the Welch t-test is somewhat general in nature (When conducting a t-test why would one prefer to assume (or test for) equal variances rather than ...
- 3,427
5
votes
1
answer
3k
views
How to compare a sample against some baseline data?
First let me describe the situation I'm dealing with:
I'm looking at performance data for a software system. I have data for many versions of the software, including ongoing. For each version I have ...
- 51
6
votes
4
answers
848
views
Estimating the probability that a software change fixed a problem
At work we have a hardware device that is failing for some yet to be determined reason. I have been tasked to see if I can make this device not fail by making changes to its software driver. I have ...
- 163