sample size calculation

  1. T

    Sample size sensitivity in time series regression analysis

    I have a time series that I've built a regression on, say Y = X + Y. For a data set of size 300, the coefficients of X and Y are statistically significant. But, the coefficients are not statistically significant for a (sequential) subset of the dataset of, say, 150 points. Now, since the...
  2. E

    Sample size calculation issues

    Hello, I have a question regarding a research project I'm working on. We have conducted an experiment where the same sample is measured over and over again to get an idea of the analytic variation in our system. We have a nice normally distributed data-set with all parameter estimates. We...
  3. S

    Sample Size in AB Testing

    Hi All, I'm a marketer trying to understand the math behind A/B testing. I understand how to calculate sample size before a test is run. I've just come across a tool that estimates how many more samples are required to reach significance for a test that's underway. Visitors Goals...
  4. A

    Sample Size Determination

    n=8, mean=5096, StDev=1460, SEmean=516.19 I need a 95% confidence interval no wider than $360. What is the minimum sample size required? I calculated this as 193, but was told I was incorrect. The issue may be with my bound, which I calculated to be 0.0706, or 7.06%. Using the formula...
  5. Z

    How do I calculate the Sample Size for this type of Survey?

    Hi all, I need to calculate the sample size for a survey I will be undertaking soon. The target population will be the clients of 8 hotels, forming part of the same company. The objective of the survey is to get the profile of the clients and their level of satisfaction. I've read that if the...
  6. I

    Using GPower3 to calculate sample size

    I ran the following calculations in GPower3 but I am doubting my method and I am looking for suggestions but also perhaps a beginners way of checking this mathematically. I have a one way test, with an r of .25 an alpha of .05 and a power of .80, I came up with a required sample size of 95...
  7. E

    Need a help for sample size calculation

    I have a database of 1500 records and I am are going to use the database for future use, if the inaccuracy of the data elements (eg. Date of birth of each record) is less than 5% (or accuracy is more than 95%). I am planning to get a simple random sample from the database and check with the...