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Questions tagged [small-sample]

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

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19 views

What are the values of a student's distribution (k, µ and σ) when x1 = 10, x2 = 10 and x3 = 10? [duplicate]

I have a sample that contains only 3 values that are x1 = 10 x2 = 10 x3 = 13 Remark: I know that x3 value is not what is written in title I will calculate the ...
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0answers
18 views

Characterization of risk factors for a very rare condition

I am looking at a cohort of patients including 13000 patients, out of which only 160 have condition A. Out of these patients, only 6 have condition B. I would like to be able to characterize those ...
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2answers
67 views

Can one make statistical inferences from 6 patients?

Is it conceptually correct to make statistical inferences from a very small number of patients (even when using exact methods like Fisher's test, etc)? What do I have to look out for: power or p-value?...
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10 views

Retrospective risk factor analysis in small samples

I am looking for risk factors for an specific outcome (death at a certain time) in a retrospective cohort of a disease. I have 40 observations and lots of variables (30+), mostly cathegorical. Have ...
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26 views

dummy variables and interaction terms: when the number of observations matters

Some authors conducted a univariate cross-section regression using 26 observations: $$Y_i = a + b \cdot X_i + e_i$$ Some others did the same regression and added another one where $X$ is split ...
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1answer
36 views

How to approach a classification problem when the sample size is only about 50

I was given a data consists of 53 people and I was asked to come up with a general classification rule based on biomarkers that can be used to classify each person under one of the three possible ...
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7 views

How to account for low sample size when computing performance?

I am interested in analyzing user performance at a per user level. Users have the opportunity to engage with an app by answering trivia questions and can choose how many questions they want to answer. ...
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16 views

Sample size calculation for parametric test, with large effect expected, small numbers. Should I use parametric or non parametric tests?

I am trying to figure out what would be the best way to analyze data from a randomized double blind trial we conducted. We sought to find if two dosages of a drug were effective for a severe symptom ...
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2answers
50 views

Inference based on a single observation

Imagine we use machine A to perform a task, we repeat it 1000 times and it always takes more then 30 min to finish the task. We buy a new machine (machine B) and in the first run it takes 29 min to ...
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1answer
29 views

How do I determine the likelihood of a single measurement coming from a known distribution? [duplicate]

I have a set of 2000 numbers that form an approximately normal distribution, with a mean of about 0.24, and an SD of 0.06. These form an estimate of the population. I now have a single sample ...
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1answer
38 views

Index accuracy based on sample size out of population size

Suppose I have people who work at different companies and I am interested in seeing their view on some topic. In order to do this, I decide to conduct interviews on people from each of the different ...
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52 views

Assess statistical significance with before & after binomial data from few participants

For the quantitative analysis of a pedagogical approach, I applied a series of (equivalent) tests prior and after lessons. I want to evaluate the reading (proper identification of sounds from written ...
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2answers
60 views

How can I analyze small sample?

I want to use multivariate OLS on a sample size of 33, but I read somewhere that the rule of thumb is that there should be at least 30 observations to fit one covariate. I want to add around 5 ...
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2answers
145 views

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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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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0answers
22 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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0answers
35 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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0answers
22 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
36 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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0answers
65 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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1answer
56 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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36 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
65 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
30 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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0answers
18 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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12 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
96 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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0answers
117 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
24 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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0answers
29 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
24 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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30 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
22 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
584 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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19 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
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
24 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
33 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 ...
6
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1answer
307 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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0answers
32 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 ...
2
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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
54 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 ...
3
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1answer
245 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% ...
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1answer
549 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
27 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 ...