# Search results

1. ### GIT with Netbeans question

Hey everyone I am using GIT with netbeans to push projects to my bitbucket. The problem is I think I somehow accidentally set it so that it commits my entire workspace. What I mean by this is when I try to push one of my projects to one repository it pushes all of them instead of just the one I...
2. ### Java Open Source Java Projects?

Hello everyone. I am a computer science and applied math double major. I want to get involved in an open source project so I can gain experience and so I have something to show potential employers that I worked on. I just created a GITHUB account and I am not an expert at using it, nor have I...
3. ### Finding a recurrence relation

Thank you everyone I just want to test the subscript feature an-1
4. ### Finding a recurrence relation

Homework Statement a) Find a rec. rel. for an, the number of sequences of length n formed by u's, v's, and w's with the subsequence vv not allowed. b) Repeat part a) but now with the requirement that there is no subsequence uwv. The Attempt at a Solution a) the first letter in the sequence can...
5. ### Estimating a proportion

I apologize. This is the first stats class I have taken, so I wanted to make sure I understand the differences between all the different cases and that I am using the correct statistic for the correct problems. It is because I am reviewing for a final. I won't post any more hypothesis testing...

thank you
7. ### Hypothesis test and finding type 2 error probability

oops yes you are right. thank you
8. ### Estimating a proportion

Homework Statement A national safety council wishes to estimate the proportion of automobile accidents that involve pedestrians. How large a sample of accident records must be examined to be 99% certain that the estimate does not differ from the true proportion by more than 0.03? Answer the...
9. ### A hypothesis test

ok I was looking at the wrong chapter of my book. It is a large sample so we use the statistic H0 : p = p0 H1 : p ≠ p0 Z = (x-np0)/sqrt(np0(1-p0)) = (258 - 505(.46))/sqrt(505(.46)(.54)) = 2.29 we reject H0 if Z > zα/2 or Z < -zα/2 zα/2 = z.1/2= z.05 = 1.645 Z > zα/2 so we reject the null...
10. ### Small sample test concerning 2 means with different variances

Thank you. hopefully the assumption that the populations are normal doesn't cause me too much trouble
11. ### Small sample test concerning 2 means with different variances

Homework Statement The deterioration of many municipal pipeline networks across the county is a growing concern. An article stated that the fusion process increased the average tensile strength. Data on tensile strength (psi) of linen specimens when a certain fusion process was used and when...
12. ### Test comparing the means of 2 water samples

Homework Statement In June 2010, chemical analyses were made of 85 water samples (each of unit volume) taken from various parts of a city lake, and the measurements of chlorine content were recorded. During the next two winters, the use of road salt was substantially reduced in the catchment...

thanks
14. ### Test concerning difference of two means

Homework Statement The following are the number of sales which a sample of nine salespeople of industrial chemicals in California and a sample of six salespeople of industrial chemicals in Oregon made over a certain fixed period of time. California: 59, 68, 44, 71, 63, 46, 69, 54, 48 Oregon...
15. ### Hypothesis test and finding type 2 error probability

Homework Statement From extensive records it is known that the duration of treating a disease by a standard therapy has a mean of 15 days. It is claimed that a new therapy can reduce the treatment time. To test this claim, the new therapy is to be tried on 70 patients and their times to recovery...
16. ### A hypothesis test

Homework Statement An independent bank, concerned about its customer base, decided to conduct a survey of bank customers. Out of 505 customers who returned the survey form, 258 rated the overall bank services as excellent. (a) Test, at level α = .10, the null hypothesis that the proportion...
17. ### Determining a sample size

since P(-z_(α/2) ≤ (X-μ)/(σ/sqrt(n)) ≤ z_(α/2)) = .95 P(-z.025 ≤ (X-μ)/(18/sqrt(n)) ≤ z.025) = .95 -1.96 ≤ sqrt(n)(X-μ)/18 ≤ 1.96 -1.96(18)/(X-μ) ≤ sqrt(n) ≤ 1.96(18)/(X-μ) [-1.96(18)/(X-μ)]^2 ≤ n ≤ [1.96(18)/(X-μ)]^2 n = [1.96(18)/(X-μ)]^2 which is what I got before if E = (X-μ) I think...

thank you
19. ### Joint probability distribution

a) fx(x,y) = \frac{6}{7} \int_0^2 (x^2 + \frac{xy}{2})dy fx(x,y) = \frac{6}{7} ((2)x^2 + \frac{x(2)^2}{4}) fx(x,y) = \frac{6}{7} (2x^2 + x) b) Fx(x,y) = \frac{6}{7} \int_0^x(2u^2 + u)du Fx(x,y) = \frac{6}{7} (\frac{2x^3}{3} + \frac{x^2}{2})
20. ### Probability a sample mean will fall in a range

ahh ok what my book actually says is use z for samples of n>30 with σ known and if σ is not known replace σ with s and if the sample is n<30 And the population is normal use t. so since my sample is large enough, my solution to this problem should be close enough?
21. ### Probability a sample mean will fall in a range

so for either of the two statistics to work, the distribution must be normal?
22. ### Determining a sample size

Homework Statement An investigator, interested in estimating a population mean, wants to be sure that the length of the 95% confidence interval does not exceed 5. What sample size should she use if σ = 18? The Attempt at a Solution the formula I found in my book is n = [(z_(α/2) σ)/E]^2...
23. ### Joint probability distribution

Homework Statement The joint probability density function of X and Y is given by f(x,y)=(6/7)(x^2+ xy/2) , 0<x<1, 0<y<2. (a) Find the pdf of X. (b) Find the cdf of X. (c) FindP(X<.5). (d) Determine the conditional pdf of Y given X = x. The Attempt at a Solution a) the pdf is what is...
24. ### Probability a sample mean will fall in a range

Gaussian means "normal" right? I am confused a bit about that. In my book they seem to use "z" for the test statistic and use "t" when the population is known to be normal. From what I can tell they are the same thing except that with z you use the standard normal table and with t you use a...
25. ### Probability a sample mean will fall in a range

Homework Statement A random sample of size n = 81 is taken from an infinite population with the mean μ = 128 and the standard deviation σ = 6.3. With what probability can we assert that the value we obtain for the sample mean X will fall between 126.6 and 129.4? The Attempt at a Solution z =...
26. ### Statistics expected values problem

Homework Statement Let X1 and X2 be independent normal random variables, distributed as N(μ1,σ^2) and N(μ2,σ^2), respectively. Consider a random variable U = 2X1 − X2. (a) Find the mean of U. (b) Find the variance of U. (c) Find the distribution of U. The Attempt at a Solution a) E(U) =...
27. ### Triple integral changing order of integration

Thank you all so much!
28. ### Triple integral changing order of integration

it wouldn't be from 0 to y/2? or wait that would only be on the xy plane? so it would be from 0 to (1/2)sqrt(y^2-z^2)
29. ### Triple integral changing order of integration

I don't want to just guess so first i want to make sure my picture is correct. This is what I have drawn:

0 to y/2 ?
31. ### Triple integral changing order of integration

ok I may be completely off but it is starting to look like part of a cone and I think the limits of integration for x will be z/2 to y/2 . then i think the limits for y should be z to 4 because z=y on the zy plane and y = 2x and then I think z will be integrated from 0 to 4
32. ### Triple integral changing order of integration

Homework Statement rewrite using the order dx dy dz \int_0^2 \int_{2x}^4\int_0^{sqrt(y^2-4x^2)}dz dy dx The Attempt at a Solution I am having trouble because i don't know what the full 3 dimensional region looks like but the part on the xy plane is a triangle bounded by x = 0 , y = 4 and y =...
33. ### Sampling distribution of mean

I got mixed up with the sample size n=20 for the 25 samples. I see the mistake now. thank you
34. ### Sampling distribution of mean

It was done for the 50 samples as an example in my book but they didn't really show the work they just said the answers and compared them. The exercise says to combine the 50 from the example into 25 and do it for those. after combining them these are the 25 values I get: 3.8, 4.3, 4.3, 5.1...
35. ### Sampling distribution of mean

Is it correct that I combine the samples like that? for some reason my variance is coming out negative
36. ### 10 card hand problem

thanks everyone
37. ### A sequence of coin tosses

Homework Statement Suppose a coin is tossed 14 times and there are 3 heads and 11 tails. How many such sequences are there in which there are at least 6 tails in a row? The Attempt at a Solution I will treat the sequence of coin tosses as a "word" where each letter is a toss and is either an...
38. ### 10 card hand problem

Homework Statement How many 10-card hands are there chosen from a standard 52-card deck in which there are exactly two 4-of-a-kinds; no pairs or 3-of-a-kinds? The Attempt at a Solution if there are exactly 2 4 of a kinds that takes up 8 of the 10 cards in the hand and the remaining 2 must be...
39. ### Sampling distribution of mean

Homework Statement suppose that 50 random samples of size n = 10 are to be taken from a population having the discrete uniform distribution f(x) = 1/10 for x = 0,1,2,...,9 0 elsewhere sampling is with replacement so that we are sampling from an infinite population. we get 50 random...
40. ### Double integral to find volume between two surfaces

Oh I think I get it now. This is the integral I came up with: \int_0^4 \int_0^{(4-y)^\frac{1}{2}} (4-x^2) dxdy
41. ### Double integral to find volume between two surfaces

Homework Statement set up and evaluate a double integral to find the volume of the solid bounded by the graphs of the equations y = 4 - x^2 z= 4 - x^2 first octant The Attempt at a Solution I am fairly confident in my ability to evaluate double integrals , but I am having a problem figuring...

thank you
43. ### Absolute extrema 2 variable function

I think I figured it out using the rational roots theorem. for the equation 2x^3-3x^2 + 1 the possible rational roots are -1/2 , 1/2 , -1 and 1 plugging them all in the only ones that give 0 are 1 and -1/2 since y = x^2 if x =1 y = 1 we already know z = 1 at this point if x = -1/2 y = 1/4...
44. ### Absolute extrema 2 variable function

Thats supposed to be a 6x^2
45. ### Absolute extrema 2 variable function

Ok i will use lagrange multipliers. The gradient of f=(2-2y)i + (2y-2x)j Let g= y-x^2 =0 Then the gradient of g = -2xi + j Multiply the gradient of g by a constant c = -2cxi + cj We must solve the system 2-2y = -2cx 2y-2x = c Y-x^2 = 0 Plug in our value for c into the first equation...
46. ### Absolute extrema 2 variable function

Homework Statement find the absolute extrema of f(x,y) = 2x - 2xy + y^2 in the region in the xy plane bounded by the graphs of y= x^2 and y = 1 The Attempt at a Solution first we find the first partials fx(x,y) = 2 - 2y fy(x,y) = 2y-2x 2-2y = 0 when y = 1 2y - 2x = 0 when y=x in this case...
47. ### Absolute extrema function of 2 variables

I think I am starting to get it. I check critical points by finding the first partial derivatives. This will give possible mins or maxs in the interior of the region. Then we plug in the constraints to get one variable functions for the boundaries of this region. i am picturing these as sort...
48. ### Absolute extrema function of 2 variables

I read it I just don't think I fully understand. So basically there is no critical point inside the interval for the function 4-2y so I just have to plug in the boundaries? so the max is z = 6 and the min is z = -1/4
49. ### Absolute extrema function of 2 variables

oops. ok so we have y = -1 |x| <= 2 f(x, -1) = x^2 - x f'(x, -10 = 2x -1 = 0 2x = 1 x = 1/2 doing the same with y=1 we get x = -1/2 so the mins are at (.5, -1) and (-.5, 1) but now I am confused because when x = -2 |y| <= 1 f(-2,y) = 4 -2y f' = -2 != 0 so there is a problem there...
50. ### Absolute extrema function of 2 variables

Homework Statement I need to find the absolute extrema of the function in the specified region f(x, y) = x^2 + xy R = {(x,y): |x|<=2, |y|<=1} The Attempt at a Solution The first partial derivatives are fx(x,y) = 2x+y and fy(x,y) = x They are both 0 only when x and y are both 0. So...