The expected value of a random variable; or a location measure for a sample.

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-3
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0answers
25 views

Given mean and standard deviation [on hold]

If you are given a mean of approximately 10, and a std dev of 1, and you need 8 data points, how do you figure out those data point values?
0
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0answers
37 views

Compute the % using SD, and Mean

Compute the percentage of crime rates that fall within one sample standard deviation of the sample mean So I have this data called 'crime rates' and I want to answer the question above, and as ...
0
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0answers
13 views

Basic application of mean, median and percentiles [closed]

The mean salary at an island t-shirt shop is \$28,400 with a standard deviation of \$5400. The median salary is \$27,400 and the 62nd percentile is \$28,900. Is the following True or False: ...
0
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0answers
15 views

Mean Rank Order Format

my apologies for my obvious lack of knowledge in the matter, however I am currently doing an assignment in which we had to conduct a mini research study in order to assess our SPSS skills. One of the ...
0
votes
0answers
8 views

Should the arithmetic mean of a subset of population data be annotated as sample mean?

If I have population data, and I want to calculate the arithmetic mean of a subset of the population data (e.g. for a certain category of values within a certain range of $n$ observations), is the ...
1
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0answers
15 views

What mean to use in odometer calculation based on model?

Im trying to figure out what would be considered a valid calculation. Imagine I have a dataset that looks like that: ...
1
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0answers
17 views

Average Difference of Averages

I'm looking at the gender pay gap across the UK using some data from the ONS. The data is released as mean and median gross pay by sex by local authority area. Figures for England as a whole are also ...
4
votes
1answer
45 views

What is the relevance of standard deviation?

I do a humanities subject but have a statistics based analysis of a rating experiment and cannot get my head around standard deviation. The rating test is 1 to 5 1) Mean: 1.7 Standard Deviation: ...
0
votes
1answer
31 views

calculating mean of a random variable raised to a power

Given the mean & variance of a dataset of linear measurements X ... N~(14,2), I want to find the mean of X^3. So by taking mean as being expected value, & rearranging: - ...
0
votes
1answer
35 views

Use of “mean” in estimating $p$ of $Bin(n,p)$?

The $p$ (probability of success) parameter of binomial distribution $Bin(n,p)$ can be estimated by deriving it from the mean: $$\mu = np \iff p = \frac{\mu}{n}$$ However, given example that r.v. ...
1
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1answer
172 views

Are Cov(A-B) and Mean(A-B) equal to Cov(A)-Cov(B) and Mean(A)-Mean(B)?

If $\mathbf A$ and $\mathbf B$ are real value matrices (sets of vectors) and $\textrm{cov}(\mathbf A)$, $\textrm{cov}(\mathbf B)$ and $\textrm{cov}(\mathbf A - \mathbf B)$ exists, are these equations ...
0
votes
1answer
30 views

Is this a valid way to calculate an SD of a pooled sample (NOT a pooled SD)?

Let's say I've got 2 different populations (e.g. 35 and 40) with 2 different means and SDs (22.3, 28.0) and n (e.g. 35,40). I don't actually know the individual values. Obviously you can calculate a ...
1
vote
1answer
43 views

How to calculate a mean of a sample where some measurements do not match a normal distribution?

I have a set of temperature measurements from amateur meteo stations around the place I live in. Being amateur meteo stations, the measurements vary because of the placement of the probe, measurement ...
3
votes
1answer
33 views

Calculate the mean of the minimum of any k samples

Given a fixed list of N numbers from an unknown distribution, and a k (k <= N), say we ...
0
votes
3answers
49 views

One tailed or two tailed situation

I understand that there is a lot of similar questions, but I can't grasp on when to use a one tailed or two tailed test when reading a example such as the one below: We suspect that test driven ...
1
vote
1answer
86 views

Confidence Levels for Mean of measured distribution

I have measured some values. These values are already aggregates (in principle average values). The values have a "non-nice" distribution, for example . They come from different sources with different ...
1
vote
1answer
63 views

minimum cdf given mean and variance

Suppose I have some distribution with mean $\mu$ and variance $\sigma^2$. How to prove that for the distribution to have min $cdf$ over all the distributions with mean $\mu$ and variance $\sigma^2$, ...
0
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0answers
101 views

How to compare means, when ANOVA is not possible?

I have the following problem. I have four samples (data are generated from four different methods that generate a graph and calculate a graph parameter), lets call them a, b, c and d, each with size ...
1
vote
1answer
81 views

Standard deviation of (assumed) normal distribution

Say I measure a system for $N$ periods of time $T$. In each of these time periods $T_i$, with $1 \leq i \leq N$, I get $M_i$ occurrences. I have reason to assume that the variable $M$ follows a ...
0
votes
0answers
19 views

Can I use an independent t-test if my data is skewed?

I want to compare the means of two independent data sets. However, both the data sets are extremely skewed right. I was considering using an independent t-test, but according to this, it's an ...
1
vote
0answers
37 views

Combine three Gaussian values with different standard deviations

I know how to combine two observed values with different standard deviations into one mean value: $$ \left(\frac{\sigma_b^2}{\sigma_a^2+\sigma_b^2}\right)x_a + \left(\frac{\sigma_a^2}{\sigma_b^2 + ...
2
votes
1answer
89 views

Alternative notation for the arithmetic mean?

Is there any alternative to the convention of using an overline for denoting the arithmetic mean? In my opinion overlines are confusing. For instance, is $\overline{\mathbf{a}}$ a vector or a scalar? ...
2
votes
1answer
36 views

Calculating actual quantile from poorly defined lognormal distributions

I have a dataset in which the uncertainties in various parameters are modelled with a lognormal distribution. After the experiment I get a single number result. As part of a lookback to understand how ...
3
votes
1answer
58 views

Sort $X$, then scale the first differences by $\bar X$: what, if anything, is this used for?

Sort data vector $X$, take first differences of the sorted data, and divide by $\bar X$. I came across this transformation in someone's notes, without any citation. It would be applied to ...
20
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2answers
200 views

Is there a reliable nonparametric confidence interval for the mean of a skewed distribution?

Very skewed distributions such as the log-normal do not result in accurate bootstrap confidence intervals. Here is an example showing that the left and right tail areas are far from the ideal 0.025 ...
0
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0answers
11 views

How to calculate the mean of scale with scale and ordinal items measures in SPSS?

I have a scale called - Facebook Intensity Intensity, with 8 items, adapted from https://www.msu.edu/~nellison/TOIL/scales.html 6 out of 8 items are SCALE Measures, but others are ORDINAL as there ...
1
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1answer
42 views

Can I divide the standard deviation of two samples to create an overall standard deviation?

I calculate a project's change order rate by dividing the cost increase by the awarded value. For example, if the awarded value is 10,000 and there is a cost increase of 200, the change order rate ...
0
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0answers
9 views

Should I look at mean performance to choose the best mean performance?

I've tested $C$ configurations for a computing platform's performance, each with $M$ runtime measures $t_{c}^{(m)}$ for re-runs. There is a spread for each configuration, due to random reasons (e.g. ...
3
votes
1answer
41 views

Confidence interval for population mean when sample is a series of counts?

I have count data for each of a sample of individuals (it's the number of times each independent individual performed a certain behaviour during a standardised observation of that individual). How can ...
4
votes
1answer
99 views

lognormal with very large mean, but small sample value

Let $X \sim N(\mu, \sigma^2)$, where $\mu = -800$ and $\sigma = 76$ Let $Y = \exp(X)$, so Y has a lognormal distribution, $E(Y) = \exp(\mu + \sigma^2/2) = \exp(2088)$, which is a very large number. ...
0
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0answers
6 views

how to estimate the loading factor for a travel company?

I am pretty naive to statistics, so please correct me where I am wrong. I am trying to estimate average case loading factor for travel company. This travel company is running shuttle service wherein ...
1
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0answers
19 views

Estimator of a normal mean: practical recommendation?

I have a sample of $n=370$ $5$-dimensional observations which can be reasonably well modeled using a multivariate normal distribution. I want to estimate the mean using this sample, which will be part ...
0
votes
1answer
68 views

Can the mean be a random variable?

Can the mean of some sample of random variables be itself a random variable? Yes?
0
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0answers
28 views

A feature of several items (likert scale) - one score is needed

Currently I am analysing the quantitative analysis data of my final Marketing project in SPSS and I have a doubt: I have conducted a survey with some questions grouped into 4 features (Trust; ...
0
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1answer
46 views

variance or variation of mean , are they the same thing? [closed]

I have been thinking about this for a long time. What are the possible variations of the mean in statistics? Is this the same as variance?
0
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2answers
33 views

repeated measures in irregular interval

I have glucose measurements of some patients who are visiting in a hospital, which is measured over 4 years time. Each of the patients have more than one record every year. The interval between this ...
2
votes
1answer
42 views

Gaussian distribution sample norm versus mean norm

Consider a Gaussian distribution with mean $\boldsymbol\mu$ and covariance matrix $\mathbf{Q}$, and suppose I take a sample from this distribution and compare its norm with the mean norm. My goal is ...
4
votes
1answer
51 views

What is the effect of taking the mean of a moments-based estimate?

Suppose I estimate the second and fourth moments of a signal as $M_2 \approx \frac{1}{N} \sum_{n=0}^{N-1} | y_n |^2$ and $M_4 \approx \frac{1}{N} \sum_{n=0}^{N-1} | y_n |^4$ and then I use these ...
0
votes
1answer
25 views

Why standard deviation of population is unknown in t test

Why mean of the population is known but standard deviation is unknown ? Mean is calculated from individual values then why can't standard deviation be calculated? Is there any practical scenario where ...
4
votes
2answers
232 views

why use Mean of posterior distribution instead of probability?

I'm reading the Think Bayes by Allen B. Downey, and on this example I don't understand well the purpose of Mean in the chapter 3.2 The locomotive problem. ...
1
vote
1answer
68 views

Bayesian vs. frequentist estimation

I don't really understand the connection between bayesian to "normal" frequentist estimation. Suppose we want to estimate the expected value of a population given a sample. In frequentist statisics ...
0
votes
1answer
30 views

How can I compare two mutual funds' performance with a sparse set of data?

I want to compare the performance of two mutual funds. The only data I have is annual returns for the past 7 years. So I have 7 observations for Fund 1 and 7 observations for Fund 2. In addition, I ...
0
votes
0answers
19 views

Statistical analysis on daily data

I have a number of data points that I am trying to extract a meaningful pattern from (or derive an equation that could then be predictive). I am trying to find a correlation (?) between RANK and DAILY ...
1
vote
1answer
25 views

How to determine a threshold, statistically?

I have a data from 6 months of 20 employees who sell cars and car insurance. I can capture the % of car insurance sold based on the numbers, but how can I figure a number(threshold) which tells me how ...
1
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0answers
21 views

Estimation of the mean when data points are not independent

When we estimate the mean with 95% confidence, this formula is used: $\hat{\mu}=\overline{\mu}\pm1.95\times\frac{\overline{\sigma}}{\sqrt{N}}$, where $\overline{\mu}$ is the sample mean, ...
0
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0answers
25 views

What is the n when calculating the standard error of the product of two independent means?

I have two independent means and I need to find the error of their product. Calculating the variance is fairly straightforward, and I already have the formula for that, but I can not settle on what n ...
1
vote
1answer
55 views

Statistical tests for variance

I have several images taken in a location every few minutes. The images depict a flooding pattern in a location which we count as number of pixels (y) vs a number that corresponds to time intervals. ...
3
votes
1answer
366 views
2
votes
0answers
25 views

1 group; 4 variables; small sample - can I compare means?

I have a small sample (n = 16) that completed 4 questionnaires. I am trying to determine if any of the questionnaire mean scores are significantly higher than the others. The data isn't normally ...
0
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0answers
19 views

Estimating SD only Mean Known

I subscribe to a report that provides prevailing prices for the last 1 week. For example I get the following information: * Number of cases : 7 * Average rate quoted : 1,200$ I know nothing else. I'm ...