Questions tagged [statistics]
Mathematical statistics is the study of statistics from a mathematical standpoint, using probability theory and other branches of mathematics such as linear algebra and analysis.
11,528
questions with no upvoted or accepted answers
-3
votes
1
answer
2k
views
What is the definition of 1 standard deviation.
I know what the standard deviation is. I know about the 68–95–99.7. My question is what is the definition of 1 (just 1) standard deviation. Why is it 68 and not 70. Is it because that's where the ...
-3
votes
1
answer
144
views
Statistics: Finding mean lifetime with given lifetimes
Given:
$P(X>5) = .7$
$P(X>15) = .343$
$P(X < 2.5) = .8367$
Find the mean lifetime.
I tried finding $\mu = 1/\lambda$, but that wasn't the correct answer. I'm not sure what equation to ...
- 79
-3
votes
1
answer
112
views
What is the t-score for the relationship between X & Y
The police chief is concerned about alarm systems degrading in city buildings and failing to operate. Using a sample of 100 alarms in operation the previous year, the police department regresses ...
- 95
-3
votes
1
answer
146
views
How do I determine percentages using the mean and standard deviation?
There are 80 terms, measured in seconds.
The standard deviation is 77.96433 (sec).
The mean is 267.2375 (sec).
What percentage are over 180 seconds?
What percentage are between 210 seconds and 300 ...
-3
votes
1
answer
40
views
Finding this probability, I need some explanation.
If green and yellow seeds per plants are crossed and $15$ seeds are obtained calculate the probability of getting $(0,1,2,....15)$ green seeds. Green is a dominant and hybrid gene, yellow is a ...
- 1
-3
votes
1
answer
279
views
Probability interval for a cost related to a Poisson random variable.
For a certain section of pine forest, the number of diseased trees per acre, Y, has a poisson distribution with mean of 10. The diseased trees are sprayed with an insecticide at a cost 3 dollars per ...
-3
votes
2
answers
987
views
confused about meaning of a expectation of a function
https://en.wikipedia.org/wiki/Bias%E2%80%93variance_tradeoff#Derivation
well,in the "Derivation" part of the wiki link.
i don't figure out why $E(f)=f$, does it imply that the function $f$ is ...
- 119
-5
votes
1
answer
80
views
How many unique combinations are possible if category contents are limited?
I'm working on a personal project and came across an algorithm problem which stumped me. I need to know whether a user has given my program the correct parameters to create the amount of random ...
- 1