Midterm 1 - Version C - Short Answer

# Midterm 1 - Version C - Short Answer -...

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Unformatted text preview: Psychology 60 – Spring, 2010 – Midterm1 – Given 4/20/10  1    Short Answer / Computation Questions:        VERSION C  For these questions, you must show your work in order to receive any credit. If you are using a  formula to solve the question, write the formula first, and then apply the formula to the problem.     Write legibly and CIRCLE your final answer for each question    1) A market researcher interested in how much individuals on the UCSD campus talk on their  phones takes a sample of 6 students and asks them to report how many minutes a day they  talk on their phone. The following are the data this researcher obtains:  45, 80, 60, 4, 18, 25   a. Find the value of SS for this sample.   Xbar = 232/6 = 38.67          X 45 80 60 4 18 25 X-Xbar 6.33 41.33 21.33 -34.67 -20.67 -13.67 (X-Xbar)2 40.11 1708.44 455.11 1201.78 427.11 186.78                                              Σ(X­Xbar)2  =  4019.33  X 45 80 60 4 18 25 Σ =232   Or       ,    12990 – 2322/6 = 4019.33      b. Assume that SS = 3800. (DO NOT USE ANY OTHER VALUE FOR SS).   Find the best estimate of the standard deviation of the population      estimated σ = sqroot( SS/(n­1) )    estimated σ = sqroot (3800 / 5 )     estimated σ = sqroot ( 760 )   estimated σ = 27.57      X2 2025 6400 3600 16 324 625 Σ =12990 Psychology 60 – Spring, 2010 – Midterm1 – Given 4/20/10  2    2) In a population of exam scores, a score of X = 86 corresponds to z = +2.00, and a score of x = 77  corresponds to z = ‐1.00. Find the mean and standard deviation of the population.                   μ =  80      σ = 3                      3) A research firm is interested in obtaining a sample of individuals who use Facebook a “typical  amount of time per day,” which they specifically define as the middle 34% of people in terms  of hours spent per day on the website.  Assume that Facebook usage in terms of hours per day  is normally distributed with μ = 4.8, and σ = 1.  Determine the cut‐off values in number of  hours per day that this research firm should use in recruiting subjects.                              p( ‐0.44 < Z < 0.44 ) = .34                               Xlower  = 4.8 + (‐0.44)(1) = 4.36 hours                         Xupper  = 4.8 + (+0.44)(1) = 5.24 hours                      ...
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