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  1. Miner

    Bias type / sorting

    I am not certain that this applies, but there are two types of bias that impact the use of multiple choice questions in surveys. They are:
  2. Miner

    Finds best 7 best days in a row out of a set of data

    Calculate a moving average of length 7, then find the max moving average. These are the lot numbers: 14438438 14438441 14438445 14438458 14438466 14443462 14443486
  3. Miner

    Not even sure how/where to start....some type of regression needed.

    Another approach that comes to mind since you mentioned you were a chemist is EVOP (Evolutionary Operations) where you make a series of small changes and follow the path of steepest ascent. I have only seen this used with 2-3 factors, so I don't know if it can be used for 6. The downside of...
  4. Miner

    Not even sure how/where to start....some type of regression needed.

    Technically, this calls for an ordinal logistic regression. You may be able to get an understanding of what is important using a multiple regression (6 IV plus some interactions). This biggest issue will be the small sample size of 11. This will severely reduce the power of the analysis to...
  5. Miner

    LIKERT SCALE - Which statistical test to use? Is a test for normal distribution necessary?

    @noetsi No, we do not have the entire population. We are probably working with 15-20% of the population, which for surveys, is an excellent response rate. I worry about theory if the problem is design or manufacturing related, but with customers, it's more about identifying what makes them...
  6. Miner

    LIKERT SCALE - Which statistical test to use? Is a test for normal distribution necessary?

    Likert scaled data presents a number of problems. I have analyzed a lot of it for customer surveys (n > 5000) and have concluded that there is a major difference between what is statistically correct and what actually works. I have found that nonparametrics based on the median will often not...
  7. Miner

    % on the population based on % of the sampling

    The level of uncertainty (i.e., width of the confidence intervals) is based on the sample size, not the population size or the percent of the population inspected. This assumes that defectives are homogeneously distributed throughout the lot and the sample was truly random. Otherwise, all bets...
  8. Miner

    % on the population based on % of the sampling

    I recommend that you post this in a quality forum as you will get better response. The two best forums are: Elsmar Cove This forum has been around a long time and is the most active The Quality Forum Online I think you are misunderstanding the use and purpose of AQL tables. You correctly...
  9. Miner

    Categorical variables in SPSS - Chi-square and then what?

    Sorry. I don't know anything about SPSS.
  10. Miner

    Categorical variables in SPSS - Chi-square and then what?

    I am a Minitab user, and it provides a "contribution to Chi-square" statistic for each cell. You then look for the largest statistic by cell. The formula for this is:
  11. Miner

    How to test the variability of count data over time

    In the field of industrial statistics, there are control charts based on the Poisson distribution that are designed to detect changes in count data. These are called c-charts for subgroups of a constant size, or u-charts for subgroups of varying size. I recently found a generalized control...
  12. Miner

    Two sets of sample

    An unpaired t-test (2-sample) may be used, but will have the drawback that the year to year variation may cause enough noise to drown (pun intended) out the differences between provinces. Does this suggest another approach that would overcome this weakness?
  13. Miner

    Two sets of sample

    What approaches have you considered? What is the part that is confusing you? Note: We don't provide homework answers, but will guide you in the right direction if you demonstrate that you are making an effort.
  14. Miner

    Time Series-Temperature differences

    There are several approaches you could try: ANOM on the monthly means & StdDev. The ANOM null hypothesis is that no mean is different from the group mean. This is different from the ANOVA null hypothesis, which is that no single mean is different from another mean. Individuals control chart...
  15. Miner

    Assessing Quadradic Data

    I agree. All polynomial models are an approximation of the true relationship.
  16. Miner

    Calculation of the standard deviation of a rate per 1000 (Work SPC Chart)

    You mention SPC chart in the thread title. If you are trying to calculate the control limits for a p-chart, you may find them here. It is the same formula that @katxt mentioned multiplied by 3. If your questions tend more toward quality and SPC than statistics in general, I recommend this...
  17. Miner

    Safety study design

    I recommend posting your question in elsmarqualityforum They have a very active discussion group for medical devices.
  18. Miner

    Statistical significance/ probability

    This is not really my strong area. My application of Chi-square is limited to less complex situations, but you did ask me, so here goes. You can organize your contingency table into a 3-way table (rows (cartype), columns (carfollowed) and layers (lane)) then perform the Chi-square analysis.
  19. Miner

    2 dichotomous IVs and one continuous DV... which test to use?

    A 2-way ANOVA should work for this provided the data were collected per the 2-way design.
  20. Miner

    Error propagation through a mean

    Is the error column truly the "Standard Error" or a stated uncertainty? As katxt pointed out Standard error is the standard deviation of multiple means. That means that each measurement (e.g., 10.1) is the average of a group of averages of multiple individual measurements. Is this what your...