The area of statistics that provides descriptions of data, may it be samples or the population. This includes graphical representations and numerical indicators. No information is inferred from samples about the population, as in inferential statistics.

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Best way to answer average question with large range of data

I have expense data for 30+ departments. I want to figure the best way to answer the question 'what is the average expense?' The problem is that each department has a different range of data and size. ...
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18 views

Statistics and data analysis

What is meant by confidence interval in data analysis e.g. 95% confidence interval? How does p<0.05 estimate significant difference?
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17 views

Does it make sense to interpret autocorrelation and box test on 5 data points?

I am trying to see if after I trade a stock the price movements at 2, 5, 7, 10, 30 and 60 seconds after exhibit any autocorrelation. Below I have the returns from my trade price to the trade 2,5,7,10 ...
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74 views

A basic probability probem

I have question and I could not figured out how to proceed solving question: I think the probability of Success for part (a) is 0.75 and for part (b) it is 0.50. I guess this is a binomial question, ...
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55 views

Variance of Portfolio of Assets

The variance of a portfolio of two assets is calculated as $Var(R_P)=w_a^2\sigma_a^2+w_b^2\sigma_b^2+2w_aw_b\sigma_{ab}$, where $w_a,w_b$ are the respective weights of the two assets in the ...
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How can the median number of sexual partners be 6.1 and 3.6?

http://www.cdc.gov/nchs/nsfg/key_statistics/n.htm Median number of female sexual partners in lifetime, for men 25-44 years of age, 2006-2008: 6.1 Wouldn't it only be able to be x.5 or x.0?
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32 views

How does a median have a value that is a decimal which isn't exactly half of an integer if the data should consist of only integer values?

I real an article which said the average man accumulated 6.1 sexual partners while the average woman accumulates 3.6. If the statistic talked about the average, surely the numbers would be equal-so it ...
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36 views

Confidence Interval Algorithm

I am trying to write a C++ program for parameter estimation(with Confidence Interval information) of an Exponentially distributed data set. I understand that $\lambda \bar{X} \sim \Gamma(n, n)$. To ...
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18 views

Skewness in a graph of data

It seems counter-intuitive to me that a graph that is skewed right actually has more data values on the left side (and vice-versa), like in this image: I don't get how the term "skewed right" ...
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13 views

Can I use several medians, IQRs, and N for each, to calculate the median and IQR for the composite group?

I have measurements of a group divided into subsets, with a median, interquartile range (IQR), and total N for each subset. I would like to calculate the median and IQR for the total group using this ...
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26 views

Is the following data set possible?

"Is it possible to create a data set where $\bar{x}=30.0$, range $R=10$, and variance $s^2=40.0$?" I feel sort of dumb asking this question, but I'm not quite sure I'm on the right track. I know that ...
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34 views

CV Percentage Error with Confidence Variable

I am trying to calculate a confidence variable (CV %) of two numbers where the numbers them selves have a confidence range. Appologies for my sloppy representation, I am somewhat of an equation novice ...
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1answer
99 views

Correctness of a statistical evaluation of a parameter

I have a question about a non-Gaussian distributed parameter that can only take certain values in a defined interval. Knowing that I have to define this parameter starting from a set of its values and ...
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1answer
11 views

What measurement should be used to determine per unit capacity of a given volume ish question

I am reselling data packages and would like to add a sense of scale to the packages. Without disputing actual numbers, an email message is between (3-20)Kbytes, a photo 270kb, a web page ...
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1answer
28 views

Correction factor for the variance

In an exercise they asked me: "Why could we use the following correction factor? $\text{varianceX} = \frac{n-1}{n}*\text{varianceY}$ What I said was basically, because the unbiased sample variance ...
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34 views

Intuition for the formulas of mode and median for grouped data

To estimate the mode and median of a grouped data set, in my Statistics class they presented these formulas to me: Mode = L + [(fm-f1) / (fm-f1)+(fm-f2)] x h where: L is the lower class boundary of ...
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16 views

Normality assumption of MANOVA

Data set has 2 dependent variables and 1 independent variable with 3 groups. Normality assumption of MANOVA says that variables has to be normally distributed within the groups. My data set has 30 ...
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24 views

Descriptive Statistics - higher level of risk/higher level of average return

I have heaps of these questions to do, so please explain your answer as thoroughly as possible so I can carry on the knowledge to the rest. Thank you. Questions below are related to this data set: ...
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40 views

How to construct a two sided confidence interval?

A machine produces metal rods used in an automobile suspension system. A random sample of 15 rods is selected and the diameter is measured. The resulting data are shown below. 5.21 5.28 5.29 5.27 ...
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1answer
50 views

P-value - test at $5 \%$ if there is significant difference in fuel consumption between the two petrol grades?

A car owners want to investigate if gasoline consumption of his car depends on the fuel octane number. He therefore intend to "premium" and "regular" at random and computes each time the ...
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1answer
27 views

(bookexercise) sign test of $H_0: \bar m = \bar 25$ against $H_1: \bar m < \bar 25$ there we have 15 known random observation

Follwing data desribes the measured fracture strength of 15 randomly selected units made by a new ceramic material $$20, 42, 18, 21, 22, 35, 19, 18, 16, 20, 21, 32, 22, 20, 24$$ At a previously ...
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38 views

determine the confidence level for the confidence interval $I_{\bar m}=(x_{(2)},x_{(9)})$

Let $x_1,...,x_{10}$ be a sample from a continuous random variable $X$ with the median $\bar m$. Determine the confidence level for the interval $I_{\bar m}=(x_{(2)},x_{(9)})$. $x_{i}$ is the ...
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16 views

Does the scale have a systematic errors?

Let B be the systematic error as $$B=E(m^*)-m$$ there m is the correct value. to determine a scale has no systematic errors you use an object with a known weight 14.4(this is te correct value?) . ...
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1answer
25 views

Covariance and Independence problem

The Random Variables $X$ and $Y$ can each take on only two values. Show that if $Cov(X,Y)=0$, then $X$ and $Y$ are independent. One can see that the distributions take the form: $P(X=x_1)=p$ and ...
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1answer
57 views

Hypothesis test: decide the test variable ic in normal distribution.

I know that the test variable is based on the estimation of the parameter. So, if we have an sample of size $n$ from $N(\mu,\sigma^2)$, $\sigma^2$ known, and want to test $H_0: \mu=\mu_0$, then the ...
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1answer
46 views

what does extreme really mean in P-value method

if $P:=P_{H_0}$(To get an equally extreme outcomes that the observed), what does "equally extreme outcomes mean then? For an example in this situation. How does he get that " When saying extreme then ...
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19 views

P-value hypthesis test(my bad - found same question in math stack) [duplicate]

textbook exercise How can I calculate P-value at a test of $$H_0: u=3.2$$ against $$H_1: u \neq 3.2$$ if we have the observations $2.0$, $3.2$, $3.8$, $2.5$, $3.3$, $2.8$, $3.0$ and $3.4$ which is a ...
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1answer
48 views

Probability that your return is positive for the week, given its distribution per year

You make an investment. Assume that returns are normally distributed with a mean return of .20 per year and a standard deviation of .10. Suppose you check on your returns once a week. What is the ...
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12 views

Question on the distribution of miles run monthly…

I am working on a project related to the habits of people who are jogging/running on a regular basis. I wonder if there are known models based on real life statistics (or else) regarding the ...
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1answer
16 views

what i am doing wrong in calculating quartiles

can somebody please help me to understand? Why 1st quartile in this data is equal 4.5 and 3rd quartile is equal 6.5. I am getting 4.25 and 6.25 , but not 4.5 and not 6.5. I use formula (n+1)/4 for ...
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19 views

Give the appropriate type of rejection regions - my attempt and questions.

Let $x$ be an observation of $X$~$Bin(n,p)$. We want to test null hypothesis $H_0: p=p_0$. Give the appropriate type of rejection regions where a) $H_1: p<p_0$ (Could need some comment ...
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28 views

selecting Rejection Regions with two-sided alternative hypothesis

Let $x$ be an observation of $X$~$Bin(n,p)$. We want to test null hypothesis $H_0: p=p_0$. Give the appropriate type of rejection regions where a) $H_1: p<p_0$ (Could need some comment ...
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1answer
33 views

The distribution of roll of a dice $12$ times

What's the distribution of a variable $X$ if $X$ represents the number of times you get outcome $k$ when you roll a dice $12$ times? I thought that the distribution was a binomial distribution with ...
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1answer
30 views

Is there a preferred statistical way to measure diversity? If not, how to go about inventing one?

I don't know much about statistics, besides a couple of humorous chestnuts, so please bear with me. Let's say I run a corporate tax law firm in Georgia with two other white guys. We have a hundred ...
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2answers
36 views

confidence intervals for 20 different parameters - distribution, probabilit and most probable value.

I need help with the subexercise (c) in the following exercise. A researcher is planning a study where she must calculate confidence intervals for 20 different parameters. The intervals are ...
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8 views

How to reliably calculate the mean (and std dev) on a circle

I want to calculate the mean (and std dev) of a number of measurements on a circle. In my case, I measured the index on a ring buffering memory chip, where a certain condition occurs, serveral ...
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1answer
45 views

Will Steve the train engineer be mad?

This is a basic Z- score question. I would just like to know if I solved it correctly. Train cars for the Crandic Railway Company carry 25 standard-sized containers. The weight of each container is ...
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15 views

Estimating Required Sample Size based on Percentages

The seeds of the garden pea are either yellow or green. A certain cross between pea plants produces progeny where 75% are plants with yellow seeds and 25% are plants with green seeds. What is the ...
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9 views

Estimating the intensity of a spatial point process ruled by a (known) external forcing field

My problem is the following. Assume a spatial random point point process (called E) on $\mathbb{R}^2$ and a continuous field $U(x,y)$ define on the same domain. The goal is to estimate the intensity ...
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16 views

Statistics on ordered lists

Participants of a study had to rank several proposition by their importance: 1st, 2nd, 3rd, and so on... Two cases are of interest for me: The "ideal" case: there are $n$ propositions and each ...
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35 views

Concrete example : likelihood, comparing theory and practice (genetic linkage)

Crossing tomato plants should give birth to a new population of plants of 4 types that we'll call $P_1$, $P_2$, $P_3$ and $P_4$. According to theory, the ratios of appearance of these 4 should be ...
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14 views

sum of standard deviation in hypotesis testing?

I am performing a test of difference between means with paired data. I have to compare the means of the time taken to complete a job that is divided in 3 different actions. I have the average time ...
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3answers
36 views

Help solving volume equation

I'm working on some ecological data that uses the following equation to calculate volume (V) of timber logs in cubic metres per hectare based on surveys along a transect. $$ V=\frac{\pi^2\Sigma ...
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1answer
29 views

Confidence interval - determining the Confidence based on pre set upper and lower boundaries.

I am trying to solve home made problem, but i am having a hard time solving it.. A Appleseller wants to advertise the average weight of his apple, but since he sells so many it isn't possible to do ...
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16 views

Prove the expression for standard deviation

Problem Let $x$ be a variable assuming the values $i=1,2,\ldots,k$ with frequencies $f_i$ and let $F'_i$ be the corresponding cumulative frequencies of the greater-than type, while $F''_i$ are ...
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1answer
45 views

If $R$ and $s$ are the range and standard deviation of a set of $n$ values, then $4\le R^2/s^2\le 2n$

Problem Let $R$ and $s$ be respectively the range and standard deviation , respectively, of a set of $n$ values. Then prove that $\dfrac{R^2}{2n}\leq s^2\leq \dfrac{R^2}{4}$. I have tried ...
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1answer
57 views

The Largest Gap

If I have an X amount of randomly generated positive numbers, what type of algorithm could I run to find the following: Precisely where the largest difference exists between two of the numbers? How ...
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16 views

Curve 'anti-correlation' detection

If I have a data set, what algorithm can I use to detect when one curve moves in clear opposition to the majority of curves? For example: At point 15, the purple line moves up in opposition to the ...
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2answers
14 views

Population Variation with two variables

I have a dataset with two variables. I want to treat my dataset as a population not a sample. I am wondering if I can just use the formula for population variance as below: ...
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13 views

Is there a measure that monotonically changes as we change a normal distribution to a bimodal distribution?

Is there a measure with values varying monotonously from -1 to 1 (or 0 to n) as we change a bimodal distribution (or say a reverse normal distribution) to a normal distribution? Will the same work if ...