# standard deviation

1. ### 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...
2. ### 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...
3. ### 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...
4. ### 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...
5. ### 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...
6. ### 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...
7. ### Hypothesis testing

Hey guys, This is my first thread on this forum so please bare with me as I try to be as concise as possible, I'll then write down my questions at the end of the thread. I'm working on some class notes, and stumbled upon this problem that confuses me on some point: "The drying time of a...
8. ### Normal Distribution of multiple Std.Dev´s and Means

Is there a way to calculate the Normal Distribution of a set of multiple Standard Deviations (SD) and Means (µ)? I am afraid I do no have Access to the raw data from which the SD´s and µ´s were calculated. Many thanks in advance
9. ### Statistical power of two dataset

Hi All, I would like to inquire how to decide whether Dataset A or Dataset B would be reliable based on their coefficient of variation, number of data points and mean value. What kind of factors could be considered? I am not searching for the direct answer but rather to jump into the...
10. ### how to get a normalized daily standard deviation from erratic data

Hi, I use Excel to analyze data. On one of my workbooks, I have about 30,000 rows of intraday data. Sometimes I might have 0 datapoints on a particular day, some days I might have 15 datapoints, and other days 20 datapoints. On average, I have about, 5,500 datapoints over the period of a...
11. ### Average and standard deviation

Hi All, I am measuring the height of a tank over time to calculate the flux. -F is the volume of tank F -On every time point, the volume is measured 3 times (since the way of measuring is quite fault sensitive) So F has an average and a standard deviation. -Flux: (F(t)−F(t−1))/dt, in which dt...
12. ### Choosing method for comparing peoples salaries

I just came to the sad conclusion that I have not been maintaining my statistical skills enough the last years, and therefore I must kindly ask for help in this easy question: How to find standard deviations from variable A for individuals in a group adjusted for effect of variable B? I have a...
13. ### I need a push in the right direction, not sure how to attack the problems..

Hi :) I am new here on the forum and find it a bit difficult to learn the way to go at different statistics/probability - problems. For the most times I am able to figure it out myself doing some research, but the last two problems has got me stuck for a few days. I would be really thankful for...
14. ### Hypothetical Statistics Question Regarding Class Curve, Standard Dev, and Mean

Theoretical question: So say there is a course where if you score two standard deviations below the mean, you will fail the course. The class average will be roughly a 75%, not sure what to set as the baseline for standard dev, and say 150 people are in the class. One person is added to the...
15. ### Dividing means and their SD to give confidence limits

Hi all, I am trying to solve the following elementary stats question, but am not sure how: "10 values were taken to calculate the mean of 'A', and 10 separate values were taken to calculate the mean of 'B': mean A = 73.5 (standard deviation 6.3) mean B = 12.7 (standard deviation 2.7)...
16. ### How to find the probability of a sampling error made in estimating the population mean?

Alright, I have been working on my statistics assignment since Monday and I only have two questions left, dealing with the probability of a sampling error. Unfortunately, I cannot find anything in my notes and only a brief example in my textbook that does not explain the concepts behind the...
17. ### Bayesian Posterior: SD = SE?

I was curious if the standard deviation in a Bayesian posterior is equal to the standard error?
18. ### It's posible to compare two means without considering standard deviations?

My doubt is the following 'it's possible to compare means of two independent groups without considering standard deviations" ? For example: Control Group: mean +- standard deviation 50 +- 10 mm Experimental Group: mean +- standard deviation 100 +- 30 mm I am very...
19. ### Posterior of a Lognormal Shape Parameter, in Terms of Prior Location & Shape

I am setting up a Bayesian analysis using a lognormal distribution with skewed data. I want to estimate the "standard deviations" of samples taken from different bins, where sample-sizes available from some bins are very large, and others are very small. I have reliable prior information...
20. ### standard deviation greater than variance, is this ok?

I am putting together some audit results and it was suggested I present them as mean +/- SD. However there is a significant variance in the results. For example looking at hours it took to achieve a targeted temperature goal : results varied from 0 hours to 11. Using excel I ended up though with...