standard deviation

  1. N

    Question Regarding Standard Deviation of Rate Vs. Time

    Hello, I am not particularly well versed in statistics but I am doing some research and encountered something I didn't understand and was hoping someone here could help. For my research, we need to find the pump speed with the most consistency when filling a vial to 50ml. I am not sure if I...
  2. P

    Variances of many series of random variables

    Hello all, I have to use some statistics in my bachelor thesis, but I had little contact before this. So I am a litte confused on how to proceed. I have about 100.000 series, lets call them Yn, of weather temperature measurements. Each containing about 50 values (X1, .. X50) and each is...
  3. N

    mean rank to mean + sd ?

    Hi everyone, We are students trying meta-analysis for the first time using revman software (of cochrane). For one of our study we are stuck because we only have the mean rank and we don't know how to convert the mean rank into mean and standard deviation to obtain our forest plot. If someone...
  4. S

    Deviation with intervals

    I'm having an issue finding a way to distribute numbers in even intervals for any set of given data. With Standard Deviation, it's easy to find 3 even intervals: 1. Over the average + standard deviation 2. Under the average + standard deviation 3. Somewhere in between both. Basically this...
  5. B

    Probability Distribution of Cars Sold

    Hi, I'm struggling with where to go with the following problem: The probability distribution below is representative of x, the number of cars sold within a single day. x = 0, 1, 2, 3, 4 P(x) = 0.1, 0.4, 0.3, 0.2 I calculated the standard deviation and mean, which I believe 0.917 and 1.6...
  6. S

    Standard deviation from ANOVA-table

    I am trying to find an estimate for σ , based on the ANOVA-table under, but I dont know where to start. Is it possible to find the estimate for σ from the residual standard error? if so, how?
  7. S

    Calculating confidence intervals for monthly data

    Hello, I am currently working with monthly data and I try to calculate confidence intervals for the monthly average. I have data from from 2010 to 2019 and there seems to be some seasonality. The statement I want to make, is: In december 2020, we expect a value of x which lies with a certainty...
  8. BeaT

    Standard Deviation problem.

    Hi everyone, I wonder if anyone out there would help me solving this one? - I've struggle with it for a few days now. Thank you so much! Bea.
  9. J

    Does adding data to a data set affect the standard deviation?

    Hi, quite a basic question here but I can't find a solid answer. If I had a data set of 10 points, and I chose to add 4 new data points to it for example, can I use the same original standard deviation? Or must I re-calculate it? Is it possible to add the new data points with a specific number...
  10. A

    Rookie finance question: standard deviation

    Hi Im kinda new to statistics and would very much appreciate some help. I have finally understood the standard deviation formula and the reason behind every step/calculation. But..lets talk about stock market. a) why does the stock market write in percentage? I had the impression that...
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  12. M

    Can I apply Standard Deviation and IQR on daily work hours?

    Hi, I'm wondering if we could apply standard deviation or IQR on our daily log on time? I have a dataset with many machine ID that has many log in records for entire month. I have removed the weekend data and left with log in data of over 1000 machines. From the dataset, each machines has...
  13. A

    Calculating SEM in test-retest study (ICC)

    Hi! I am involved in the writing of a thesis, where two raters are running a test-retest study to test the intra- and inter-rater reliability of a clinical test. Here the Standard Error of Measurement (SEM) needs to be reported, and the following formula should be used: SEM=SD x √(1-ICC). I...
  14. M

    Estimated standard error

    Why is it ok to estimate the population variance with the sample variance formula (i.e. the unbiased estimate of the variance). I understand how we can build a confidence interval using the central limit theorem and the following formula . But, the unbiased estimate of the variance means that...
  15. CharlotteSirot

    Test temporal change in standard deviation

    Very dear geeks :cool:! I am new in this forum. I am a french post-doc in marine ecology and I am especially interested in trophic relationships. I am currently analyzing time series. I have to admit that time series are definitely one of my strongest Achilles heels, I am actually afraid of...
  16. B

    Aggregate precision of a measurement instrument based on a sample of measurements whose true errors are known

    I want to estimate the accuracy and precision of aggregate data from an instrument that measures a variable that fluctuates over time by comparing a sample of its measurements to concurrent measurements made by a reference instrument. For this purpose, assume that the reference instrument...
  17. B

    Standard deviation of three producttypes

    Hi guys!. I need some statistics help here. I have three producttypes; Plates, spoons and mugs This is what i know Spoons: Mean = 565,87 Variance = 50677,28 Standard Deviation = 225,12 Correlation with plates= 0,8394 Correlation with mugs = 0,8271 Plates: Mean = 1806,83 Variance...
  18. D

    Back-calculation (a posteriori) of the minimum sample size for a mechanical experiment

    Hello, I want to back-calculate the minimum sample size for a mechanical experiment. I have a known mean and standard deviation of a statistical population. From the statistical population I chose two samples with means and standard variances I could estimate. My question is: How can I...
  19. J

    Calculation of overall ranking from mean, SD, and Z score

    Hey everyone, I was hoping someone could help me. Im applying for a job, and am trying to work out my overall ranking in two seperate exams so that I can include this in the application. Could someone please tell me if my calculation is correct? I have attached the file with my calculation...
  20. D

    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 observation has been reported as a mean & a standard deviation. I do not have access to the underlying data. I am curious about whether the samples are statistically different from each other as far as...