Material: Back pain prospective cohort study of n=200 patients all suffering from LBP at the initial consultation. A questionnaire is filled at time=0 years and time=10 years. The outcome is back pain (VAS score 0-10), disability (RMDQ 0-23). Patients are divided into two groups based on MRI-finding with +/- disc protrusion at time=0 years, group sizes: +disc protrusion n=80...

Biostatistics for pain study, NP t-test or GLM ?]]>

In my science class, we had to record the amount of time it took for an ant to escape 4 different colored mazes to see if color had an impact on escape time. In determining the statistical significance of the differences in escape time for the different colors, would a one-way ANOVA be correct to use?]]>

I would like to calculate the standard error of my Dependent Variable. However, I have psycholinguistic data, which uses multiple ppts and multiple items. Thus, there are 2 ways of doing this: either by calculating SE over averaged responses (example 1) OR by calcualting SEs over raw responses (Example 2)

1. Average over items by participant (as in Table 1). Then calculate mean and SE from this table.

Table 1.

..which gives mean 62.67 and SE = 16.63

2. List...

Calculate Standard Error over averaged responses or raw responses?]]>

Two players take part in a task where they each attain a score that, for ease of explanation, is between 0 and 100.

Say these players had each done this task multiple times and I know the mean and standard deviation of the distribution of scores of each player.

Is it possible...

Who is most likely to win, and exactly how likely?]]>

Is it statistically correct to calculate a regression with overlapping areas? I have market areas as the spatial unit with different sociodemographic and (macro)economic variables and I´m examining their influence on insurance demand. The market areas are overlapping in some areas. According to the spatial distribution I suppose there´s a spatial autocorrelation. Firstly I can calculate simple multiple linear reg. and then run the Moran I. test to check for spatial...

spatial regression with (partly) overlapping areas]]>

Can anyone help me understand this?

Consider the four observations from de Normal Distribution with variance equal to one $y_1 < 10$$, y_2 > 10 $, $5 < y_3 < 10 $ and $ y_4 = 10$.

The likelihood function is?

Would be:

$ \prod_{1}^{4} \frac{1}{\sqrt(2\pi)}\exp{-\frac{(y_i - \theta )^2}{2}}$

Replacing:

$(\int_{-\infty }^{10}\frac{1}{\sqrt(2\pi)}\exp{-\frac{(y_1 - \theta )^2}{2} dy}) \cdot (\int_{10 }^{\infty}\frac{1}{\sqrt(2\pi)}\exp{-\frac{(y_2 - \theta )^2}{2}...

Inference Statistic - Likelihood Function]]>

Then, I take a draw, and observe it is equal to 0.7.

Is there a way to calculate the probability that it was generated by one distribution or the other?

Thanks!]]>

I am learning about data science at the moment. I want to calculate the 95% confidence interval for the amount of Long-Term Debt that I could expect to have with Long Term Assets of $50,000,000. I calculated a regression analysis for the impact of long-term assets on long-term debt below.

I had to two ideas to come up with the confidence interval. I would appreciate your help which one is correct!

Lower...

Excel 95 % confidence interval]]>

I have e little dataset of biological data (concentrations) collected over a geographic range of 1000 km grouped in 4 spots (ca. 100 km each).

Given the tiny sample (2*25 samples corresponding to two different time periods), I thought about Bayesian methods and a MCMC approach in order to compare potential geographic clines between the two periods.

My question is rather simple : is it possible and if yes, how could I do that in R please ?

Many thanks to all the folks that could...

Few Continuous data irregularly dispersed over geographic range]]>

I have a data-set which consists of 1 continuous (although it can be discrete if I choose to round up the values) dependent variable Y and several categorical and discrete data columns that may or may not have an effect on Y.

Y, in this case, is not normally distributed so to check if a given categorical data-column/independent variable has a significant effect on Y a Kruskal-Wallis test can be used.

However, my objective is to find out which categorical data-column is the most...

I have a data-set with 1 continuous independent variable and several categorical variables, how can I find the most important categorical variable?]]>

Some brands were consumed more than others, and therefore had more respondents.

I have attached a representation of the table including imaginary base sizes.

I have the respondent data...

Can you use factor analysis on a table has count data?]]>

Not sure which test I should be using. I have five years of data from one city that lists all the individuals and if their income is low, medium, or high.

If I want to test if there is a significant change over time on the number of people under each category (low, medium, or high), should I be using Chi square test?

I.e. is there significant change in the number or percentage of individuals who has high income in that city.

Thanks in advance.]]>

The way I would read those sentences, they are clearly incorrect. Look at the last...

Mistake in a textbook: What proportion of studies make "wrong" conclusions?]]>

I'm struggling with some statistical concepts for a survey I'm implementing. I'm planning on using SAS for this.

Here is the problem:

I have to check a large company geo database in the field . That is, the company have many kinds of equipments (about 20 kinds and millions of each) spreaded all over the state and I have to check and see how representative that database really is. (check if the equipment exists and if it is of the same kind they claim to be)

That state is really big...

Best techniques for surveying large populations]]>

My theory is that each measurement from each patient is dependent on the volume measure for each patient. I just cannot figure out which statistical measures to use.

The attached excel file is an example of my measurements and the volumes. All numbers beneath patients simulates the measurements.]]>

rmaModel<-lmer(DIVERSITY~YEAR+(1|CIRCLE),data=data)

anova(rmaModel)

Type III Analysis of Variance Table with Satterthwaite's method

Sum Sq Mean Sq NumDF DenDF F value Pr(>F)

YEAR 4.4674 4.4674 1 672.72 31.328...

Coding and Visualizing Repeated Measures and Mixed-Effects Models]]>

For example if I get the following recored values: 1,2,3,10,11,12,13 my rule will be - [1,2],[10-13]

I create the possible ranges of data online, that means that every record of data may change the existing rule.

For example: I get the following record values one after the other: 1,2,3,2,10:

First the ranget will be [1], then [1,2], then [1,3] then still [1,3] and then ([1,3],[10])

In each...

Confidence in a rule]]>

This is my first experience with repeated measures ANOVA and mixed linear models. Since I did not found an example that uses a design similar to my experiment, I hope I can get some help. I collected 3 soil samples (SAMPLE_ID) in 4 areas (SITE), totaling 12 samples. My objective is to show the effect of a modified protocol (TREATMENT) for soil samples, considering the variability between the different areas. Thus, each sample from each area was submitted to the original protocol and...

Protocol comparison: repeated measures ANOVA and mixed linear models]]>

- I have a list of 100-200 items or so, maybe more, and I want to predict a value for each.
- My data...

Looking for the best way to use my available data in a predictive model]]>

I'm looking for outliers in many small (n=4) data sets. I have run

In one example:

Data: 33.700 30.485 29.867 29.921

G= 1.48231, Gcrit= 1.125, t-crit=1.603567

Therefore the 33.7 point is a higher outlier - but that's as far as I've been able to understand...

How do I calculate a P-value for a Grubbs test?]]>

One group is larger than the other (n=40, n=10), the data is not normally distributed. The grouping criterion is based on physical aspects and is not randomized.

I want to look at difference over time within the groups, and also between the groups. Suggestions on how to do?]]>

I have a question regarding the use of SPSS (i.e. its capability) to execute a Fisher's Exact test for large, sparse RxC contingency tables. I would like to test whether or not a certain correlation exist between my rows (diagnostic groups) and columns (laboratory tests) (see below).

Currently, I have a contingency table of 7 rows and 9 columns, that includes the data of 164 patients. Rows consist of certain diagnostic groups (e.g. different neurological diseases grouped together...

Is a Fisher's Exact test in a 7x9 contingency table feasible?]]>

Any recommendations - I don't want to be confined to a logistic based models, if there are better options?

There is obviously...

Continous (Ordinal) Outcome with Middle Group as Target]]>

I m conducting an analysis with more than 150 groups of participants (each group corresponds to a week with different number of participants). I would like to find statistical significance among the groups regarding a specific biomarker. Furthermore, i would like to spot the groups (weeks) with the statistically significance. I m using SPSS but i cannot do this for over 50 groups. Does anyone have an idea which is the best way to do in SPSS or to propose me another solution? Thanks in...

Comparison of more than 100 groups!!!]]>

So my question is can you specify a model in PROC GLM with dummy variables and then specify the same model in PROC REG, using the parameter estimates from PROC GLM and the diagnostic tools in PROC REG.

I have doubt this works, because PROC GLM treats dummy variables as dummy variables...

PROC GLM]]>

Factor analysis with nested data]]>

Is it necessary to check for multicollinearity of explanatory variables in logistic regression?]]>

I have a prospects direct mail file and I'm testing a new message, (One change). To ensure it’s the message change and not the differences in the files that drive my results I want to make sure that the test and control files are similar / not significantly different from each other for my key...

Test & Control File Selection - Help]]>

I'm running some numbers for a friend who makes instructional videos for different industries (using machines, certain tools, etc.). He has about 100 videos he's tried to sell, and has given me the number of downloads for each video, the different categories they fit into, and the price per video. For the categories, each video can be classified into a max of 3 main categories with 23 different classifications (1=laser lathe, 2=3d printer, 3=laser sander, etc.,). Each video is...

Need help with picking a test]]>

I need some help.

I have two variables, one with negative and positive values (let's call it A), and the other with solely positive values (let's call it B). I would want to do the correlation between these two variables. These values are those of individuals (one value per individual). I would like to know if this makes sense to correlate directly with the two variables, or to look the correlation between A and B in two groups : one where individuals have negative values...

Correlation]]>

Following is my experimental condition -

I have chronically treated normal cell line with smoke condensate for 12 months. Over the time the cells have changed their morphology and characteristic. They have transformed into cancerous cells - the cells morphology has changes (shape/size), they have gained all the characteristic of cancerous cells. To characterize the changes I have carried out genomic and proteomics analysis. But I am confused now - whether to use paired or unpaired t...

Paired vs unpaired t test]]>

I'm currently writing my thesis on motor inhibition, using TMS. I haven't touched the stats required for a long time, and I found it difficult to find solid answers that make sense to me in the many text-books I perused.

The dependent variable of interest is MEP amplitude (continuous).

The IVs are cue condition(3 - maybe stop left, maybe stop right, no cue), hand(2 - left, right), and timepoint(go signal, shortly after go signal).

I am trying to establish whether MEP...

3*2*2 Repeated Measures ANOVA - How to follow up a significant two-way interaction]]>

In a research project I am doing, participants are asked to compare two texts and select which text they find easier to read. Each participant will be asked to do this ten times. There are 25 texts, from which a random subset of two texts will be presented each time.

When downloading the data from Qualtrics, it is presented as a long row per participant, showing which texts are shown and which text is the 'winner' of both. However, to perform a Bradley-Terry analysis, the data should be...

Transforming columns in SPSS/R]]>

A question regarding correlation]]>

Someone can explaine me way the process

I am new to this forum and i am in need of help regarding the Holt's Winter Method. I've managed to build a forecasting model in excel using the Damped method which works very well.

But due to my lack of experience, I am confused on how to continue the raw data as the forecasting formula requires a data point to work.

My time series is volumes per week per year, historically i was linking the current week back to last years week to repeat some raw data (Bootstrapping?) (linking...

How to continue raw data for Forcasting ~ Holts-Winter]]>

A study that investigates whether one drug is not inferior to another (noninferiority study) can conclude that the drug is superior?

"Clinically significant cancer was detected in 95 men in the MRI-targeted biopsy group, as compared with 64 of 248 in the standard-biopsy group (adjusted difference, 12 percentage points; 95% confidence interval [CI], 4 to 20; P=0.005). It, was noninferior to standard biopsy, and the 95% confidence interval indicated the superiority of this strategy over...

Non inferiority study]]>

I have a dataset containing of number of flowers and a number of fruits produced per year by a certain clonal plant. The research was done for 2 vegetative seasons, the measurements were done on 10 sample patches in the research area (see the picture attached). The success of the sexual reproduction will be shown as a frequencey fruits/flowers in a certain patch/season. I have the frequencies calculated, now I would like see if there are significant variations between patches and...

Which test to use? - Research on sexual reproduction of a clonal plant]]>

I have a between-subjects 2(group: low vs. high) x 5(condition: c1, c2, c3, c4, c5) design. When running the ANOVA I find a significant group*condition interaction, so I therefore want to decompose this analysis by using a simple effects approach to locate the root of the significant interaction term (i.e. I want to look at the effect of condition at each level of group).

I...

Simple main effects - alpha correction]]>

Trend test for comparing brain size]]>

1.)

[Relative Standard Deviation (%)] Question on Suitability]]>

I have ~700 patients. I used SPSS version 24. I first wanted to check if there is a correlation between the troponin level (numeric/continuous) and several other lab parameters for each patient - some are numeric/continuous and some are numeric/ordinal (e.g. white blod cell count, hospitalization days, etc..). as the troponin levels did not follow normal distribution, I used

Am I using the right statistical tests?]]>