Mehdi Azizmohammad Looha

15 Questions 46 Answers 0 Followers

Questions related from Mehdi Azizmohammad Looha

What is the appropriate random effect model for following data and question?

I attached a data here called image_study. The “image_study.csv” dataset contains data from a study examining the speed of classification of two different types of image: artworks, and natural...

05 June 2021 4,910 2 View

Why I get different probabilties each time I train the support vector machine (SVM) model?

I am using the e1071 package to train an SVM model with the argument "probability=TRUE". I then use "predict" with "probabilities = TRUE" and get the probabilities for the data point belonging...

20 February 2020 2,790 5 View

If my sample is large, can I use parametric statistics with a non-normal distribution of the data?

I have large sample (just one sample with 1100 cases) and I want to test a hypothesis about comparing mean of my sample in the two groups (each group has 550 cases). Some statisticians told me...

26 July 2019 3,343 62 View

How can I compare the "mean" of a variable in its two categories (when they are not noraml)?

I have a simple an common question. In summary, I have a data which has a variable named "A1" and a "group" with two categories. The "A1" variable is not normal in total, nor in the group levels...

26 July 2019 9,167 4 View

What is the rule for the single terminal node in the decision tree classificaiton?

I have a data with 12 predictor variables and one class variable. In the our method, I had to prune the decision tree with the best cp criteria. However, my output showed that there is just a...

04 June 2019 1,230 2 View

How can I handle missing data in questionnaire?

I need some simple methods to impute missing data in a questionnaire.

30 May 2017 9,108 9 View

Does the following qqplot confirm the normality assumption?

There are two test groups including formal and informal. In formal, we refer to statistical tests, and in informal, we mean graphs. When the sample size is large, the smallest departure from...

01 January 1970 1,303 6 View

How do I perform a mediation analysis in analysis of covariance (ANCOVA)?

I have four variables including a pre-post variable (two columns), a group variable (X), and two mediation variables (Z1 and Z2). How can I perform a mediation analysis in ANCOVA? What...

01 January 1970 7,064 3 View

How many covariates can I use for propensity score matching to analyze the impact of a specific drug on death outcomes among COVID-19 patients?

In my study, I am using propensity score matching to balance the effects of covariates on the impact of prednisolone on death outcomes among COVID-19 patients. 92 covariates have been considered,...

01 January 1970 8,839 5 View

What is the minimum sample size for Functional Principal Component Analysis (FPCA)?

01 January 1970 5,706 6 View

What is the difference between estimated marginal means (EM means) and Post Hoc in SPSS?

A sav file of the dataset is attached. "Yields" is the dependent variable, and "Soil" is the independent variable. The ANOVA was used to compare the mean of Yields across Soil groups. Both post...

01 January 1970 6,078 3 View

How does a non-significant effect become significant after adjusting for other variables in a regression model (or Cox regression model)?

There is a study on the impact of HIV on mortality in patients with COVID-19 (Article link: https://www.thelancet.com/journals/lanhiv/article/PIIS2352-3018(20)30305-2/fulltext). According to...

01 January 1970 1,987 3 View

What is the best alternative for ANCOVA when the assumption of homogeneity of regression slopes has been violated?

What statistical method can be used in this case?

01 January 1970 8,215 4 View

Recommendations for a high-performance laptop for Python programming and big data analysis?

What are the recommended specifications for a laptop to handle big data analysis using Python programming? I'm looking to invest in a new laptop and I want to ensure that it can handle the demands...

01 January 1970 3,063 4 View

Which laptop is recommended for data science and managing large datasets?

Which laptop is recommended for data science and managing large datasets among the following options? MacBook Pro MPHG3 - 2023 (Apple) ROG Strix SCAR 18 G834JY-N5049-i9 32GB 1SSD RTX4090...

01 January 1970 2,971 3 View