# Cheat Sheet Stats

Good Essays
2673 Words
Grammar
Plagiarism
Writing
Score
Cheat Sheet Stats
Chapter 3
Standard units tell you how many standard deviations above or below average a data value is standard units = (actual value – average)/SD actual value = average + (SD x standard units). Standard units are denoted by Z.
Chapter 8
Complement rule: P(A) = 1 – P(A doesn 't happen)
Multiplication rule:
P(A and B both happen) = P(A) x P(B given A happened)
Q. 5 random components removed one at a time from box containing 5 defective and twenty working. What is chance of selecting all defective:
A. 5/25x4/24x3/23x2/22x1/21. Selecting no defective 1 minus chance of selecting all defective or 20/25 x 19/24 x 18/23 x 17/22 x 16/21 = 2/7 or 29%
Q. Important data server breaks down 40% of the time, is operational the other 60%, and servers breakdown independently. How many independent servers should be running so that there is a 99% chance at least one is operational? (40%)^X = 1% (1% = chance none are operational)
A. .4^5 = .01024, so to get to .99 uptime, add another server.
Q. Consider two bonds with BB- ratings, chance of default 1.5%. What is the probability that both default within a year? A. .015 x .015 Q. What is the probability that neither defaults? A. .985 x .985 Q. What is the probability that exactly one defaults? A. P(exactly one) = 1 – P(neither) – P(both) = 1 - .015 x .015 - .985 x .985.
Independent: P(firm B defaults given A defaults) = P(firm B defaults) = .015
Dependant: P(firm A and B default) = P(firm A defaults) x P(firm B defaults given firm A defaults). = number greater than .015
Q. Janice has noticed that on her drive to work there are several things that can slow her down. First, she may hit a red light at a particular large intersection, which happens 30% of the time. If she hits the red light, 40% of the time she will have to stop for the commuter train. If she does not hit the red light, she only has to stop for the commuter train 20% of the time. we know P(red light)=.3, P(train| red light)=.4, P(train| no red

## You May Also Find These Documents Helpful

• Satisfactory Essays

The sample mean was found to be 142 thousands of an inch. The standard deviation was found to be 3.78, while the standard error was found to 0.563. The measure of 0.114” (step 3) was classified as an outlier after thorough examination because it completed deviates from the rest of the data and also because it does lie between 99% of the other values.…

• 419 Words
• 2 Pages
Satisfactory Essays
• Satisfactory Essays

Tdistributions-test to see if variable A = variable B interval/ratio data/normal curve either they = each other or they do not-Mean of A/ Mean of B…

• 273 Words
• 2 Pages
Satisfactory Essays
• Satisfactory Essays

* Law of Expected Value: E(c)=C , E(x+c) = E(x) + C, E(cX) = cE(x)…

• 547 Words
• 3 Pages
Satisfactory Essays
• Good Essays

The standard deviation is the factor that is used to divide by in the equation. the bigger the SD,…

• 402 Words
• 2 Pages
Good Essays
• Satisfactory Essays

Standard Deviation The standard deviation σ is defined as the square root of the variance…

• 279 Words
• 2 Pages
Satisfactory Essays
• Satisfactory Essays

| The Ready Light Company produces a flashlight, which is perfectly reliable except for two components: the battery, which has a random failure rate of one in every five hours of operation; and the light bulb, which has a random failure rate of three in every ten hours. If the company includes a backup light bulb with each flashlight, what is the probability that the flashlight will perform reliably for one hour (excluding light bulb replacement time, if any)?Answer…

• 12660 Words
• 51 Pages
Satisfactory Essays
• Satisfactory Essays

a. Simulate the emergency calls for 3 days (note that this will require a “running”, or cumulative, hourly clock), using the random number table.…

• 398 Words
• 4 Pages
Satisfactory Essays
• Good Essays

The Standard deviation is a measure of the variation (or spread) of a data set. For a variable x, the standard deviation of all possible observations for the entire population is called the population standard deviation or standard deviation of the variable x. It is denoted σx or, when no confusion will arise, simply σ. Suppose that we want to obtain information about a population standard deviation. If the population is small, we can often determine σ exactly by first taking a census and then computing σ from the population data. However, if the population is large, which is usually the case, a census is generally not feasible, and we must use inferential methods to obtain the required information about σ.…

• 466 Words
• 2 Pages
Good Essays
• Powerful Essays

13. A system consists of 2 components, each of which must activate if the system is too active. One component has a reliability of .99. The other has a reliability of .95. What is the overall system reliability. (.95)…

• 864 Words
• 4 Pages
Powerful Essays
• Satisfactory Essays

sx=standard error of mean=s/square root of n= 0.7522 = ( 4.45 /square root of 35)…

• 1079 Words
• 5 Pages
Satisfactory Essays
• Good Essays

S2= 1/n-1i=1n (xi-) is called a sample variance ,and its square root s is called the sample standard deviation .…

• 3342 Words
• 14 Pages
Good Essays
• Powerful Essays

The mean is the sum of the values, divided by the total number of values.…

• 1571 Words
• 7 Pages
Powerful Essays
• Satisfactory Essays

the variance is the average of the squared differences between mean and number (the standard deviation is the √variance)…

• 588 Words
• 3 Pages
Satisfactory Essays
• Powerful Essays

The standard deviation is square root of a result of the sum of squares of differences between scores and the mean divided by n – 1 (Again in this problem n=10). Therefore, the standard deviation (s) is written mathematically as: 1)(1002−−=Σ==nxxsiii…

• 839 Words
• 4 Pages
Powerful Essays
• Powerful Essays

Standard Deviation s – The variance s2 of a set of observations is the average of the squares of the deviations of the observations from their mean. In symbols, the variance of n observations X1, X2, …, Xn is…

• 2571 Words
• 11 Pages
Powerful Essays