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Questions tagged [descriptive-statistics]

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.

Descriptive statistics is the process of using and analyzing statistics that quantitatively describe or summarize features of a collection of information.

Descriptive statistics is distinguished from in that descriptive statistics aims to summarize sampled data rather than use the data to learn about the population that the sample of data represents. Hence, descriptive statistics, unlike inferential statistics, is not developed on the basis of probability theory.

Measures used to describe a data set include—

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Find the $90\%$ confidence interval for a measurement with mean $78.1$ and SD $20$.

Here is the full problem: A calibration laboratory has been measuring a one-kilogram checkweight by the same procedure for several years. They have accumulated several hundred measurements, and the SD of these measurements is $18$ micrograms.…
Nonymouse
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What is the equivalent of a z-statistic for a textual variable containing discrete values?

I have a variable in my data which contains discrete values which have no canonical order, e.g. Apple, Orange, Pear. These values appear with a certain frequency in my base sample. I have a subset of my sample which contains the same variable, and I…
Simon
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Why squaring the multiplier in a Rank Order scoring

I wanted to ask you about a rank-order scoring technique. It seems to make sense but I am not sure that I understand the reason for squaring. It must take into account the fact that there were a total number of choices and respondents selected one…
BobT
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Finding the mode (descriptive statistics)

I have 5 classes : [0,4[ containing 4 people (density 1) [4,6[ containing 8 people (density 4) [6,7[ containing 2 people (density 2) [7,10[ containing 9 people (density 3) [10,12[ containing 2 people (density 1) The class with highest density is…
user63008
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Are all numbers in (20;30] 50th percentiles and medians of set of numbers {10,20,30,40}?

(Here I implicitly use the exclusive definition of a percentile) Let’s assume that we have following set of numbers: {10,20,30,40}. The median of this set is the mean of 20 and 30, namely 25. But here is a problem: Our median is basically 50th…
KarmaPeasant
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Normalize descriptive stats for comparison

I hope it is not a trivial question. I have data for a machine learning experiment from 2012 to 2018. In 2012, the samples are far different from the ones of 2018. Each sample is a little distribution and I think that the descriptive stats (like…
Ezarate11
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normal distribution, mean = 80 and standard deviation = 5. score? separates the top 10% of the scores from the lowest 90% of the scores

Checking my work: M = 80 SD = 5 X = ? scored 90% better than others. Closest area from table was .8997 giving a z-score of 1.28. using the formula z = (x - M)/SD, my answer is 86.4
S. Smith
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Statistic Class Boundary

I have a set of data in exclusive form. The Time(class limit) is from 0-20, 20-40, 40-60, 60-80 and 80-100. The frequency in bracket of each classes are as follow 0-20(f=2), 20-40(f=15), 40-60(f=20), 60-80(F=10), 80-100(f=3). I was asked to find…
Sasha Bambi
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Relationship between Var(X) and Var(Y) where y(i) = ax(i) + b

This is a question that appears in our textbook. "Let a and b be constants and let y(i) = ax(i) + b for i = 1, 2, ..., n. What is the relationship between Var(X) and Var(Y)?" We have then that Var(Y) = a^2(Var(X)) by the simple proof that can be…
Delonjnaidu
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Determining Null Hypothesis and use of Confidence Interval

My statistics test review question asks the following: "An ad claims that more people prefer S coffee to P coffee. A random sample of 90 coffee drinkers is conducted and out of these 90, 48 of them like S better. However, the survey person…
user163862
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What is the appropriate metric for these two values?

For a test suite I have, each test has a failure rate (from 0 to 1), where 1 means it fails every time and 0 means it never fails, and a duration in ms (this is unbounded). I want a metric (I think either multiplication or division) that will…
Michael Hagar
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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. If I take the average of everything the answer…
collarblind
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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 cases (10 in each group) so I took a look at…
user23709
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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 minimum number of progeny you would need to grow to…
Athena
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Need help understanding the approach to this question

At a meeting of information systems officers for regional offices of a national company, a survey was taken to determine the number of employees the officers supervise in the operation of their departments, where X is the number of employees…
Katie
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