normal distributed

1. t test or ANOVA for my survey results?

Hi all. I ran a survey where I showed 2 ads to men and women in 5 different countries to see which they preferred. I want to know if gender or country influenced the selection of a particular ad preference. The data is normal. I was told to use a One-way ANOVA but I don't think this is correct...
2. Uncertainty about normality (Q-Q Plot)

Hey everyone, I've done several linear regression. Now I would like to test if my residuals are normally distributed. That is how my Q-Q Plots look like: But I'm not sure what to make of the Q-Q Plots. Most of them are pretty much on the line, except for the beginning and ending. What do you think?
3. How to create a subset with a normal distribution

Hello, I have a presumably easy question for you, but I am a real newbie in statistics, so please be patient. I have a data set containing N values that more or less follows a normal distribution. I need to select N/10 values among them, creating a subset with the same distribution. How can I...
4. Distribution of fixed effects

Hi all, Let me shortly introduce my research: I am looking at whether companies outperform each other in investments. To do this I observe them at multiple investments, and calculate fixed effects. Afterwards, I tested the fixed effects to confirm whether at least one company outperforms...
5. Distribution of X+Y of a bivariate normally distributed (X,Y)

I need to give the distribution of $X+Y$ and $X-Y$ knowing that $(X,Y)$ is bivariate normally distributed with marginal means 1, marginal variances 1 and correlation $p=2$.Is it right that the marginal mean are simply $E(X)=1$ and $E(Y)=1$ ?I don't see where I should start knowing that.
6. [SPSS - wilcoxon/paired t test] - not normally distributed data

Hello! I ran an analysis of my data of research into a repeated measures design and found the difference of both conditions to be not normally distributed. When exlcuding data to make it normally distributed and thus use parametric tests, can we only exclude data that exceeds the limit of...
7. How to use the Z-test or T-Test given the sample of a non-normal population

Hi Everyone, I've tried my best to stay away from forums because I like to try to learn things on my own, but this is the third assignment I've had in this class and I'm baffled by it. I don't want to copy it verbatim in case the prof is watching. We are given the sample data of non-normal...
8. How do you define a statistical way to ensure that the worst case are captured??

I need a recommendation which addresses the variability of results. There is variability associated with these results. What I specifically need is help to define a statistical way to ensure that the worst case is captured, which can then be used in future testing and we can be sure that we...
9. Regression analyses and mediation with not normally distributed control variable HELP

I am measuring the relationship between an IV and DV and whether two other variables mediated/predicted this relationship. All are normally distributed. I also collected the 'age' of the participants as a control variable, which turned out to show two distinct sample populations (18-25, and 26+)...
10. QQ plots

Hello! This is the first time I post to the forum. I'm a numismatist working with ancient Greek coins. I'm trying to examine the normal distribution of the databases I created: c. 25,000 coins. For this reasons, I QQ plotted coins from my main database (c. 8,200 coins) versus those from...
11. Determining p-values, significant cutoffs and false discovery in non-normal data

Hi, I have a set of data points from a genetic study. I wish to ascertain which of these data points is statistically significant. The data is not normally distributed. Values can range from zero to the low thousands, with there being a large number of zero values. At present, I am using...
12. Standard deviation as a percentage

Hi i'm new here and have a really quick question, How do you interpret a standard deviation given as a percentage (in this case 20%)? I need to use the variance in further calculations (working out type i and ii errors), the data is normally distributed, and the sample size is 30, i have...
13. One Sample T-Test

For an exercise is received speed measurements on two road points. The cars drove along an urban road (30mph) that opened into a rural road (60mph). The speed measurement of each car is taken 200 meters before (speed1) the end of the urban area and a second measurement 600 meters past (speed2)...