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Questions tagged [small-sample]

Refers to any statistical complication or problem due to having few data.

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Statistical power calculation parameters - single cohort study

I am writing a study protocol using a single prospective cohort study of patients affected by advanced pulmonary cancer. Eligible patients will be administered a treatment x. The primary objective of ...
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44 views
+50

MANOVA with variables from different datasets

I conducted several experiments where I have one underlying independent variable (tree species, IV). Each of these experiments gave me one dependent variable (DV), like bark pH, rugosity or the water-...
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14 views

If a dependent sample (pre/post) is not paired (no link between pre & post) are they treated like independent samples? [duplicate]

Trying to run some tests on pre/post survey questions from a small pilot group of n=9. As a fault of the survey, there was nothing to link participants from pre to post. I'm trying to determine what ...
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1answer
28 views

95% limits of a normally distributed parameter

How do I find the 95% limits of the population distribution of a normally distributed parameter? I've taken the mean and SD from 10 different readings of the parameter. Will the 95% limits be mean +/-...
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21 views

Alternative test to paired t-test? [duplicate]

I need to compare data from paired groups, but my distributions are non-normal, and my sample size is small. Are there any tests I could apply? I've been looking into non-parametric alternatives like ...
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8 views

Data synthesis approach for sample sample prediction

I have to forecast sales of a temporal SKU which only sold one month in a year. I have sales figures for nearly 1000 different sales locations. Moreover, my data is limited for only 3 years. So I ...
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0answers
29 views

Estimate unknown sum of iid random variables

Let $X_1, X_2, \dots$ be a sequence of independent and identically distributed discrete random variables with common mass function $f_X(x)$ defined for when $x \in \{0,1,\dots,N\}$ and $N$ is known. ...
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13 views

Sample Size Adjusted Metric for Calibration Curve

I'm creating a model that provides a predicted probability of an event happening. I am using calibration curves that plot predicted probability (x-axis) versus the actual event frequency (y-axis). I ...
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1answer
34 views

What if you don't reach the optimal sample size?

I have used a binomial sample calculation to conclude that we need a sample size of 150, which for a response rate of 80% there is 80% power that the confidence limits between 71% and 89% cover our ...
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1answer
102 views

What can I infer about a correlation based on another correlation that shares one variable?

I have three vectors, $X$, $Y$, and $Z$. Each element of $X$ is independently normally distributed $X_i\sim N(0,\sigma^2_X)$. The elements of $Y$ and $Z$ are jointly normally distributed: $\left[ \...
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55 views

sufficient subsample size for given sample to obtain same regression

I am performing an engineering analysis to find out the effect of earthquake on concrete buildings. Analysis applies earthquake forces on building model for 50 earthquakes, resulting into separate 50 ...
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28 views

sample and subsample regression coefficient comparison

I have a bivariate sample size of 50. OLS regression of these samples results into line: y=β0+β1x+e. I want to know if statistically similar line can be regressed with less number of data points. Is ...
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1answer
51 views

Dealing with small sample size

The objective is to classify a variable Y which is binary, outcomes [0,1], where all the features $X_1$....$X_{156}$ are normalized and continuous. The methods I'm using are Logistic regression and ...
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29 views

What is the minimum number of observations required for percentile calculation?

Here it is stated, but not justified, that percentile calculation requires at least three observations. However, in this book the authors say that it depends on the percentile value (e.g., for the ...
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0answers
13 views

Method of calculating an average from statistically insignificant sample

I am collecting weather data from a region that has a 10 weather stations placed around it. The stations collect data such as temperature highs and lows, amount of precipitation, etc. Some of these ...
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1answer
39 views

Build a statistical model based on small sample size

I hope my question is not too wide and that this is the right place to ask it. I'm working in the field of spectroscopy and chemometrics. I'm building a statistical model to predict pollution levels ...
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0answers
16 views

Small sample size using proc mixed and can't include treatment and visit interaction term

I'm analyzing data from 2 treatment groups with repeated collections at month 1, 2, 3, 4, 5 and 6. I'm interested in the treatment difference at month 6 (e.g., using the LSMEANS statement in SAS). ...
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0answers
20 views

algorithms for high dimensional data in a small sample size

I am trying to analysis high-dimensional data in a small sample size and I meet a problem: First,I divided all samples into two sets: training set and test set. Second, in the training set The Y is ...
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20 views

Exam results - is there a statistical difference?

I have exam results from one group of students - typically small size sample 1 to 3 students - vs. a larger group who took the same exam. I have scores on a range of 0 to 15 with most being between 8 ...
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16 views

Conducting a Pilot Study without Large Sample

I want to obtain preliminary evidence that some experimental manipulations I would like to use in research have a good chance of being successful (i.e., successfully manipulating the intended ...
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11 views

Weak Sample Size & Low Statistical Power

I have a problem of sample size for my research paper approval. I could only ran the statistics on 5 subjects for both plantar pressure and temperature measurements but the statistical power seems to ...
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0answers
68 views

Model Validation Firth Logistic Regression r

I am modeling Neilsen Ratings based on an AnAttr using Firth Logistic Regression using R using the logistf Library. Typically I use Pearson's Hosmer and Lemeshow in SAS to test model fit. I am ...
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39 views

Determining Sample size of Unknown Population Standard Deviation

I am trying to determine the sample size for 95% confidence interval. I am a bit confused how to compute the sampling error. My proportion of events of interest is 0.45. The Z-value will be 1.96 but I ...
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1answer
23 views

checking the equality of variances when we have very small data sets

I have two groups with very small sample sizes. Each group has around 6 observations. I was wondering which test I can use in order to check the quality of variances? Is there any cutoff value in ...
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28 views

Feature selection in the presence of extremely large feature set

Suppose you have a very large feature set (1000s to 1000,000 features) when building a machine learning model. How do you go about selecting the features? I know of the following methods for feature ...
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1answer
21 views

Test set error estimation under a small sample size

What are some of the plausible approaches to estimate the test set error when you have a very small sample set available (specifically, when the small sample size does not justify using a hold-out set)...
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29 views

(Re)-Train on a small dataset and new incoming data

I would like to train a classifier (doesn't matter which learning algorithm) on a small set of training data. As soon as the system predicts new samples, it should collect them, add the samples to the ...
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7 views

Motivating the exclusion of certain results based on sample size

A survey of the physical condition of cars on the road is taken every year. A random sample of those cars is selected each year. The number of cars selected each year changes. Most years the sample ...
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20 views

Is having cumulative samples a problem?

We are running a marketing campaign where we send out comminications to a select group of customers on daily basis. The customers are different each day. However each day we only have a small number ...
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1answer
18 views

Confidence interval for the mean of a bounded non stationary random variableb given N samples

I have a random variable bounded on [0,1]. The mean can be modeled as a random process. Assume the change of the mean |mu_i - mu_{i+1}| is bounded with a known bound. Given N (N is not large) samples (...
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1answer
517 views

A huge gap between training and validation accuracy, confusion with the concept of Overfitting

I have a fairly small dataset with 100 examples per class and 12 classes in total. Out of all the CNN models I have tried, the only inference I could make is that my training accuracy plateaus at 97%, ...
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0answers
18 views

Average variability of small data set

I have data for 300 devices and each device has been tested a different number of times so some devices have 2 data points and some have 8. For example, one device scored 5, 6.5, 6.5, 6, 6, 6 whilst ...
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0answers
11 views

What is the appropriate testing methodology for a one-to-many control test for store sales uplift?

I have a situation where from a whole bunch of stores, two have been given a treatment that is expected to increase sales. For each of the two stores a control group of ten stores has been deduced ...
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36 views

Sample size and significance

I conducted a series of multiple linear regression analysis to estimate the effect of a treatment. The sample size variates from 100 to 500, while about 10 covariates are included. Since I had no ...
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1answer
21 views

Validating models on small dataset with imbalanced classes

At this moment I'm trying to predict adverse events for the next 8 hours in hospital patients receiving a certain type of treatment, using python and pandas. Every row in my dataset represents one ...
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1answer
30 views

Can taking into account all observations composing few data points help to mitigate small-sample problems?

I conducted a pilot study in which I measured a variable on 20 different days in order to document how time passage affects this variable. I want to plot the uncertainty for each day, but I have a ...
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0answers
9 views

Statistical analysis of discrete events of random occurrence and magnitude

Let's suppose I decide to try search the desert for nuggets of gold. The value of the nuggets may follow some unknown distribution, and the occurrence with which I find them is also unknown. I spend ...
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1answer
306 views

How to report: large sample sizes (10000+), significant small difference (1%)

It is known that with large sample sizes, even a small difference could be statistically significant although it may not be practically meaningful. For my current analysis, the difference in the ...
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28 views

How can I determine the likelihood that a population proportion is >= a threshold value, given a small random sample?

I want to be able to determine the likelihood of the proportion of a population being equal to or greater than a threshold value, given the result from testing a small random sample. For example, I ...
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1answer
19 views

sample size/ clinical trail

I was reading a paper that used a clinical trial method to look at the efficacy of a drug to prevent TB. The exposed group was compared to a placebo group. The problem is that each group was made up ...
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1answer
42 views

How to conduct confirmatory factor analysis with small sample size?

I plan to conduct a confirmatory factor analysis, wherein there are 12 observed variables and 3 latent variables. My sample size is 30. However, I read that to conduct a factor analysis, the sample ...
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1answer
171 views

modelling rare events with small sample size

I have a dataset of 600 observations and the target variable is binary(risky/ non-risky). The constraint I have while modelling is that the target variable is very imbalanced .i.e only 12 (only 2% ...
1
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1answer
411 views

Linear Regression with a small sample size

For part of my Masters project I want to analyse the the relationship between the age of some log piles and their invertebrate diversity. I think that I will need to do some sort of regression ...
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0answers
12 views

Which is the most suitable analysis for a multiple case time-series nested data? Combining variable centered and Person-centered approaches

I am planning a project in order to study a change mechanism within psychotherapy sessions. I am considering 8 variables to build a model. I have access to data from 10 patients, who have completed ...
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26 views

How far can I go with data-augmentation [closed]

I just started with machine learning. Actually I am creating my fist cnn with a own dataset. I've crawled 1200 images from google. hammers, screws, pliers and saws - so 4 classes. I know this data set ...
4
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1answer
229 views

Oversampling: whole set or training set

I have a rather small dataset of 4 000 points (140 features) to feed to a NN binary classifier. The problem is only ~700 of them represent the second class. Is it more common to resample the whole ...
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0answers
35 views

Choice analysis small sample size

I am looking for an appropriate statistical test for investigating significance of the differences between popularity of choices made by subjects. I would be also interested in investigating the ...
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0answers
26 views

Intuition behind low optimal # variables per split (mtry / max_features) during random forest tuning?

I was wondering if anyone might be able to provide some insight regarding how to interpret the results of some random forest hyperparameter tuning I am performing. The training set consists of: 1000 ...
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0answers
15 views

Statistics - two sample independent t-test unequal sample size

Hypothetically speaking, if I was conducting an independent t-test and my two samples had different sample sizes, let's say sample A had 21 data points and sample B had 52. what would the n value be ...
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1answer
19 views

Making a random sample from data

I intend to use the following data of patients with liver/wo disease in my research: https://archive.ics.uci.edu/ml/datasets/ILPD+(Indian+Liver+Patient+Dataset)# But there wasn't any information on ...