Data Science Stack Exchange
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Questions tagged [mean]

14 questions
4
votes
1 answer

Mean of mean and average

In order to establish an overall rating for a product from a series of user ratings (from 1 to 5), I thought that the median would be a good idea so that extreme values would not have too much influence. But in doing so, it is hard to rank products…
Gulliver
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2
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0 answers

ANOVA for mean difference b/w groups abnormal distribution, large sample size

I have $10$ groups - sample size $n>700$: resampled to $710$ for ANOVA - visually these distributions are not normal, slight bimodlity in the sets. I ran an ANOVA, and got a $P\approx 0.089$. It coincides with what I expected from the histograms,…
Bertrand Wittgenstein's Ghost
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1
vote
1 answer

Is it bad to average several MAEs calculated from chunks of a big test dataset?

In my regression problem, I am using Mean Absolute Error (MAE) as a metric for my network. My test dataset is too big to fit in memory, so I am reading the test dataset in chunks and then Keras' evaluate() the chunk. with…
ihavenoidea
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0
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0 answers

Find variance from 2 variances of 2 datasets with difference sizes

In an attempt to find the mean number of hours his tutorial classmates spent per day preparing for tutorials, John collected data from 10 of his friends in the tutorial group and found that the mean is 2.4 hours with a standard deviation of 0.8…
Lucifer
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0
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1 answer

dividing Mean by standard Deviation meaning

I have played around with logistic regression a little using movement data intervals that are prelabeled as either resting or active. I now found that if I divide the mean movement of the individual intervals by the intervals standard deviation, the…
DataVader
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0
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1 answer

mean and variance of a dataset

I have a simple question. Please see the below screenshot : It is from a midterm exam from a university : https://cedar.buffalo.edu/~srihari/CSE555/exams/midterm-solution-2006.pdf My questions is how the means are postive ? I am asking because the…
Ahmed Mohamed
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0
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1 answer

finding the mean for each of the channels (RGB) across an array of images

How can I find the mean for each of the channels (RGB) across an array of images? For example train_dataset[0]['image'].shape is (600, 800, 3) and len(train_dataset) is 720 meaning it includes 720 images of dimension 600x800 and 3 channels.…
Mona Jalal
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0
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How to find a probability distribution the parameters of which do not impact each other like mean and variance in normal distribution do?

I need to find a probability distribution to fit my data. My data has two important features, duration and activity count. Duration means how long one sequence lasts and activity count means the number of activities in one sequence. I want to draw a…
Feng Chen
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0
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1 answer

Degree of freedom. Two sampled test

According to this blog/article: To calculate degrees of freedom for a 2-sample t-test, use N – 2 because there are now two parameters to estimate. What parameters are they talking about? 2 means: for group 1 and mean for group 2? Or something…
Excentricitet
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1 answer

Combination of groupby and mean methods

I am looking at the below csv file : We have the question : Display the mean of the variable gre by group of admitted/not admitted students, using the combination of groupby and mean methods. I would write : df['gre'].mean(df.groupby('admit'))…
evinda
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0
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1 answer

What should the target variable (y) look like here?

I am doing some data science problems for practice, and this is the question I'm currently tackling: Given a list of L values generated independently by some unknown process, we will use the mean of L to predict unseen values generated by the same…
Kristada673
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0
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1 answer

Sampling a data based on average and variance of another data

I have a set of textual datasets that have the following average and variance tokens lengths: Dataset1 avg = 28.18, var = 393.03 Dataset2 avg = 32.70, var = 644.79 Dataset3 avg = 36.94, var = 805.50 Dataset4 avg = 28.56, var = 436.86 Dataset5 avg =…
Minions
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0 answers

Compare standard deviations in different samples?

I have some data which you can group based on different variables. I know how to test if they have significantly different means. But what the deviation inside the samples?
Borut Flis
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-1
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3 answers

Why mean and median are similar for well distributed dataset?

I've read that when considering well distributed variables, median and mean tend to be similar, but can't figure out why mathematically this is the case.
PwNzDust
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