normal distribution

1. Measuring the presence of a correlation

1. Given a frequency data set (collected from 10 users by letting them watch certain videos and asking some questions about the videos) how do I determine any correlation between two variables (Correctly guessed and Correctly memorized) and calculate the significance level? Video...
2. Calculating the average variance of several normal distributed variables

Hi, I have the following problem. I'm trying to average several normal distributed variables. To make it more easy, I'm using z-scores. The mean of the average is (Mx1 + Mx2 + Mx3)/3, in this case 0. But how do you calculate the variance? If I assume they are independent, am I...
3. Plotting a normal distribution curve over a histogram

I'm trying to plot a normal distribution curve over my histogram but I can't get my code to work for the curve. It just looks like it's plotting a very low curve, what am I doing wrong? This is my code: minutes<-c(107, 116, 127, 126, 111, 90, 125, 124, 92, 121, 131, 137, 95, 101, 101, 111...
4. Applying Normal Distribution

So here is the question followed by what the steps I took to solve it. Please let me know if I have done this correctly: Question: The time needed to complete an exam in a particular college course is normally distributed with a mean of 80 minutes and a standard deviation of 10 minutes...
5. t test or ANOVA, ? normal distribution

I have an experiment on cancer cell lines. There are 7 cell lines. Each cell line is treated with a different concentration of the same drug. The average concentration that killed half the cells in each cell line is calculated, along with a standard deviation as follows: Cell Line //////...
6. distribution of ln(X) when X is binodal normal

Hi everyone. I am trying to find the distribution of ln(X) when i know that X is distributed as a binodal normal distribution, in other words: X \sim p \cdot N(a,\sigma^2) + (1-p) \cdot N(b,\sigma^2) which I suppose also can be written as X \sim N( (p, 1-p) ( a, b)^T , \sigma^2)...
7. Use Normal Distribution and Chi-square distribution

My question is as follows: If X and Y are independent random variables, X has a normal distribution with mean 2 and variance 4, and Y has a chi-square distribution with 9 degrees of freedom, then find "u" such that: P(X > 2 + u√(y) = .01 note: "√" stands for square root Anyway, I...
8. How to calculate the probability between two normal distributions?

Using the normal distribution. Let X  N(1, 2) and Y  N(2, 3) where N(μ, variance) denotes the normal distribution with mean μ and variance . X and Y are independent. Let U = 2X + 3Y . What is the mean of U? What is the variance of U? What is P(6<=U<=7.5)? What is P(X>Y)?
9. Confidence Intervals for Pairwise Independant Normally Distributed Samples

Good day, I have been thinking over this exercize for a couple of hours now and I have trouble finding a starting point. Suppose that X1,i iid∼ N(µ1, σ²), X2,i iid ∼ N(µ2, σ²), that the samples are pairwise independent, and that σ is known. Derive a 1 − α conﬁdence interval for µD = µ1 − µ2 I...
10. t-test on percentage

Hi all, Pretty simple question: I have two mean performance scores in percent, one is 70% +/- 3(SEM) and one is 95% +/- 1. Someone said I shouldn't do a t-test to compare these since data can't be normally distributed. Is that true? How would I compare these means then? thanks!
11. Normal distribution theoretical moments

how we can show that the follwoing equility holds E[(x-\mu)\sigma]=0 E[(x-\mu)^2\sigma^2-1]=0 E[(x-\mu)^3\sigma^3]=0 E[(x-\mu)^4\sigma^4-3]=0
12. Standardizing a normal variable

I am trying to understand the binomial distribution, normal distribution and standard normal distribution using the attached excel file. The example in use is calculating the distribution of a random variable X which is equal to k successful shots out of n trials in basket ball. The...
13. Test whether the SD of multiple normal distributions differs between two genes

Hi, I am comparing data on gene expression between two different genes that have been tagged with GFP. Gene expression is measured using flow cytometry so that gene expression is a continuous variable along the x-axis, with counts on the y-axis. For each gene I thus have a normal distribution...
14. area under curve normal distribution

Two issues, that I am confused about after reading statistics books. Example: weight of an adult is normally distributed with mean of 180 lbs and std dev of 20 lbs. 1) is the area under the curve equal to 100% or would the area be equal to the mean? The descriptions I see in statistics...
15. Combining standard deviation/normal distribution (do I have this right?)

I have a variable with a mean of 52% and a standard deviation of 2.5%. However, the 52% mean was derived from an opinion poll which itself has a 3% margin of error, which I take to imply a standard deviation of 1.53%. Assuming a normal distribution I can calculate from the former a 21% chance of...
16. Case control, lot of parameters, N and n-Normal dist. Which test and data expression?

Firstly, my english are not so good, sorry. I will be very happy if someone help me. I am doing a case-control study, people with and without schistosomiasis. How may I perform the Kolmogorov-Smirnov test, my groups must be together or not? I think that they must stay together. Then, I...
17. Correlation between normal and exponential

Can anybody give me some pointers to how to compute confidence intervals for Pearson correlation in the case (X,Y) where X is normal and Y is exponential? I cannot find it anywhere (usually just bivariate normal) - and I guess that this case is common enough to be described somewhere!
18. Using ANOVA for comparing perceived emotions in reaction to an embodied agent

Hi there, I stumbled upon an interesting paper on "The Influence of Emotions in Embodied Agents on Human Decision-Making" by de Melo, Carnevale & Gratch. Basically they ran and experiment where they used different versions of an embodied agent (a cooperative vs. an individualistic agent) in a...
19. Normal distribution

Hi, I am working with a microarray dataset. The database contain values on 208 probes for 58 subjects. The readouts for each probe is an arbitrary unit from 0 to 5000, according to the intensity of fluorescent light detected by the slide reader. I log-10 transformed the data. Now, I am...
20. Normal Distribution times constant

I can't seem to find anything about this on the web. If I have a random variable distributed Normally: x ~ Normal(mean,variance) is the distribution of the random variable still normal if I multiply it by a constant, and if so, how does it affect the mean and variance?