# probability

1. ### Is P(x) = P(x | y )*P(y) + P(x | ~y )*P(~y) according to Bayes theorem?

Can anyone tell me if this equation valid? If yes how? I have tried to check on google but couldn't find it! If this equation is valid then I will be able to solve a question on Bayes theorem. Thanks!
2. ### Finding Variance in Poisson distribution question

Hello! Can anyone tell me how to solve this question? Consider that X~ Poisson(μ) and P(X > 0) = e ^−1.5 Find the variance? I need P(x =0) to use the formulae of Poisson distribution. But I don't have that!

I started my studies in statistics and was given an exercise, which I have a problem with: On average, one woman in 70 is pregnant. A pregnancy test has been developed. However, the test sometimes gives false results, i.e. it detects a true pregnancy in 97 out of 100, and in the absence of...
4. ### Probability of choosing 4 sick people from 100 where there is a probability of 8.6% for each of them to have a disease.

I have the following task: There is 4% of sick people in a population. There is 5% chance for a positive test for a healthy person. There is 2% chance for a negative test for a a sick person. We tested 100 people and 4 had a positive test. What is the probability of such an outcome? So far I...
5. ### A statistical test to determine strength of correlation (or probability of certain outputs) over three timepoints

Hello, New to this forum and bit of a stats newbie so forgive me for any if my question is too vague or I say anything incorrect. My dataset is ELISA outputs for 10 individuals over three timepoints with sample size. I want to see if the individuals remain in the same order over the 3...

I need to write an original question. I will use your answer as a guide to write an original question by myself. I couldn't find a guide or some examples from books or videos. I would reallly appreciate if you know and let me know where I can also find some examples . I dont know where or how...
7. ### Conditional probability

Hi! I'm working on a binomial conditional probability question and I am stuck. I would really appreciate some help. The question is as follows: You have a box of n=40 bolts. The probability of a bolt being faulty is p=0.005. You are told that at least one of the bolts is faulty, and asked: What...
8. ### Having a girl the same as AT LEAST one girl? CONFUSION!!

It’s a combinatorics project for my beginner stats class. I’ve done the project several times and keep getting it wrong. The question reads: “ Is having a girl the same event as having AT LEAST one girl?” AND then it asks me: “Is it possible to calculate these probabilities?” This project is...
9. ### Expectation with confidence

Hello, It has been a while since I used my probability and statistics. My question is: Say a group of 5 five people need to find the similarities between two foto's individually. After checking the result is that they found 3, 6, 2, 8, 1 correct similarities. How can you say with a certain...
10. ### Developing a 64 Card Poker Deck Variant - Curious About Probabilities

Straight Variant: The only difference is that the top rank can bridge the 1st rank to form a sequence. Think of it as if Q, K, A, 2, 3 was a legal straight. How is that calculated? A More Complex Straight Variant: This one gets trickier, I think. In this variant, there are: 64 cards 4 suits 13...
11. ### Galton Watson branching process

Using Galton Watson branching process. Assume that a fox had 0,1,2,3 offspring with probabilities p0,p1,p2,p3 respectively. find the probability distribution for G1 and G2. below is what I’ve done so far I think this is correct for G1 however I’m unsure where to even start with G2.
12. ### Sensitivity of a diagnostic test

There is an exercise that I am not able to solve: Diagnostic tests A1 and A2 are used to detect the presence or absence of a disease. The results of A1 and A2 are a priori independent of the presence or absence of the disease. A1 and A2 have sensitivity Sen1 and Sen2, respectively. A new...
13. ### Validate my algorithm with probability?

Before I start I wanna say sorry. This post might a bit vague, I'm not really sure where I'm going and it's been a while since I took a stat class. I'm hoping someone can nudge me in the right direction here, kinda lost at the moment. We have an algorithm for correcting people's height - it's...
14. ### Probability given an occurrence rate (small airplane fatal accidents)

Hi All, I would like to know if the method I’m using to calculate a probability based on an occurrence rate is correct or if there is a better method to use. Here is some context to give you an idea of what I’m working with: I am looking at determining the probability of a fatal accident...
15. ### Sports outcome probability

Hello! Here is the scenario I have: In ice hockey, team A is ahead at the end of the 2nd period (they have games of 3 periods for those who do not know). When team A is ahead at this point in the game, they go on to win 75% of the time. When team B is losing at the end of the 2nd period, as they...
16. ### Multi-roll, 12 sided die outcomes (used brute force 725,000 die rolls)

I have forgotten my grad school probability and need some help with the following. I am trying to create a .xls that I can use to look at the odds of multiple dice throws. Quantity of dice = 10 (n) # of sides per dice = 20 (s) Each dice has the following colors instead of numbers: 4 Yellow...
17. ### How do you put a Distribution in a Risk Analysis?

In conducting a Probability Risk Analysis or statistical risk Analysis, for example over the actions of nature for a particular period of time and for a particular geographical location, one is expected to put a distribution over all the actions of nature and choose the action that maximizes...
18. ### Probability Over 2 Sequences Of Trials

Hey everyone! I'm coding a program that identifies appearances of a lowercase "x" in a base64 encoded string. Like the following: DWADCrxV+PhR4zxkQrIMUtarkN11aitHI8DEnzyG19CD... I know the probability of finding at least one "x" in a sequence of 10 chars. My doubt is about dealing with...
19. ### Probability of Vehicles and Pedestrians meeting

Hi, I need to produce a probability for a vehicle and a pedestrian meeting along a 1km road. Here is what I know: •1km road •cars take 3 minutes to travel •pedestrians take 12 minutes to travel •30 cars an hour •20 pedestrians an hour The cars and pedestrians may also be grouped or evening...
20. ### Quality Control/Probability Problem

A production engineer has designed a system to remove sugars from a liquid product. Each product must contain an amount of sugar less than or equal to 12g. The engineer randomly samples 3 products and finds the sugar contents to be 4.5, 3.7, and 3.2g respectively. The sample mean is 3.8g and the...