0
votes
1answer
41 views

probability, normal distribution mean [closed]

Should I use a certain table for this question or should I use a special formula. A random value has a normal distribution with the mean 102.9 and the standard deviation 4.7. What are the ...
2
votes
1answer
44 views

I need help with this review question. Business Calculus/Statistics

The question is: The scores on a test have a mean of 100 and a standard deviation of 8. A personnel manager wishes to select the top 60% of applicants. Find the cutoff score. Assume the variable is ...
0
votes
2answers
45 views

Normal Distribution Problem

The time taken for a computer to connect to a server is normally distributed with a mean value given by 3.3 seconds and a standard deviation of 0.66 seconds. (a) A computer is said to have a fast ...
0
votes
0answers
50 views

Probabilities and Estimation of average and standard deviation

I've done a good bit of this number but I have trouble with part 2. I'll show you my work and the questions I can't figure in bold. A guy has a machine that scans his apples. The machine rules are : ...
0
votes
0answers
37 views

Standard Deviation ( Sort of ) Problem

I have a bunch of particles spread over a 2D area. I plan to fit a a distribution to describe the spread. To start off : I have about 100 particles arranged in a circular pattern in a "unit" ...
0
votes
3answers
85 views

Using Least Squares method to determine unknown variables

Hey guys my next test is coming up and my professor gave us a study guide that we "should" be able to compete. Here is one of the questions I don't know how to attack: I dont just want an answer. I ...
0
votes
1answer
31 views

Standard deviation / Bell Shaped Distribution

In a forest, it is known that the circumference of 10 year old oak trees when measured three feet above the ground is 20 inches with a standard deviation of 4.5 inches. It is also known that these ...
2
votes
1answer
49 views

Standard deviation and intervals

I'm working on some homework and I'm stuck on a question that is not making sense to me in terms of my answer. The question states: ...
2
votes
1answer
60 views

Chebychev to get at least 90 %

Im am given a list of integers and asked to give the interval that contains at least 90 % of my values. Values : $62,56,72,83,66,77,62,71,50,58, 74,81,76,67,70,70,69,67,80,81, ...
1
vote
1answer
34 views

Confidence interval and normal distribution

For question (a), is the answer 0.7143? For question (b), is the answer 10.85 and 11.95 ?
0
votes
2answers
496 views

Finding Missing Observed Scores given standard deviation and mean

The question that i'm being asked it: the mean of 10 observed scores was 20 and the standard deviation if 6.0. the observed scores are {16,11,20,24,29,24,16,20,,} what are the two missing scores I ...
0
votes
1answer
19 views

Interquartile Rang concept / Problem?

If a set of data consists of only the first ten positive mulitple of $5$, what is the interquartile range of the set ? I have tried to solve but my answer is wrong..
1
vote
1answer
77 views

Finding 'symmetrical range' from mean.

A machine used to make butter where its masses are normally distributed with mean m and standard deviation s.It is found that 5% from these butters are having mass more than 85g where else 10% are of ...
0
votes
1answer
71 views

Explanation for correlation coefficients and standard deviation rolling 3 dice

Roll in MATLAB 500 times threesome-dice (3 dice) and sum them.Find in addition: max and min in each sequence mean values of sum/min/max. deviations of sum/min/max. correlation ...
1
vote
2answers
9k views

to calculate standard deviation using mean and sample size [duplicate]

Given the mean as $1336$ and sample size as $24$, how to calculate standard deviation when the deviation scores and sample figures are unknown.
3
votes
3answers
825 views

7.7 standard deviations away from the mean?

I'm confused. I have a problem where I have to find the probability that x is below the z value 7.7. My z table only goes to z values of 3.4. How do I calculate this? These are the hints my teacher ...
0
votes
2answers
180 views

Compare Standard Deviation

The Obama vacations have cost an average of 4 million and a standard deviation of 5 million. The Bush vacations have cost an average of 3 million and a standard deviation of 2 million. What is more ...
0
votes
1answer
84 views

Standard Deviation and Variance

Since the start of the Obama presidency, the average number of minutes playing golf each week is 160 minutes and the standard deviation is 20 minutes. The average number of minutes attending cabinet ...
1
vote
3answers
185 views

Simple standard deviation question using stocks as example

The following table is from page 171 of Fundamentals of Investing (11th edition) by Gitman, Joehnk, Smart. Please consider only the X, Y and XY columns (second, third, fifth). Portfolio XY comprises ...
0
votes
2answers
3k views

Calculating missing data points from standard deviation and mean

I have to figure out what to missing data points are from a set of 10 scores. The mean of the 10 observed scores is 20.0 and the standard deviation is 6.0. The observed scores are listed below, with ...
1
vote
2answers
2k views

Which is a better measure of uncertainty: standard deviation or resolution uncertainty?

Let's say I take a ton of measurements of the diameter of a marble with a 0.001" resolution micrometer, and I calculate the standard deviation of the sample set. Would the standard deviation be a ...
1
vote
1answer
1k views

Standard Deviation vs Standard Error

I am confused about the difference between standard deviation and error. When do I use which? From my lecture: Standard deviation quantifies spread of data about mean Standard error measures spread ...
1
vote
1answer
226 views

Effects of subtracting numbers in a set of random variables on their mean and standard deviation

This is a question about linear combinations of independent random variables. X and Y are independent random variables. $X$ has mean 2 and standard deviation 4. $Y$ has mean 3 and standard deviation ...
0
votes
2answers
70 views

How can I figure out a set of values that most of my population will hit 99% of the time?

I am not a math person, I'm trying to put together a spreadsheet in excel that takes the square footage for every property in a county as the only input. I want to then generate a list of square ...
1
vote
0answers
632 views

Can't find Standard Deviation for Continuous Random Variable

Here is my homework problem. Again, sorry for the formatting: A continuous random variable X has a symmetric distribution with mean 18. A brilliant mathematician has estimated that the probability ...
1
vote
3answers
600 views

Chebyshev's theorem

OK, so here's the question (not my homework - which is line segments -_-) According to Chebyshev's theorem, how many standard deviations from the mean would make up the central 60% of ...