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A few theory questions

  • 19-05-2008 1:24am
    #1
    Peyton Manning
    Closed Accounts Posts: 16,658 ✭✭✭✭


    Just need help with a few of these questions, would really appreciate it, but consider it a challenge to yourself ;)

    1. When would you use the median rather than the mean as a measure of central tendency?

    2. "The Retail Price Index (RPI) is something of a compromise between a Laspeyres and a Paasche Index". Explain this statement.

    3. What do you understand by the term "statistically significant"?

    4. When two variables are correlated, can you be sure that one variable causes the other? Why or why not?

    and finally,

    5. You are given the following data:

    Hours of Study (X)..........20.....16.....34.....23.....27.....32
    Examination Mark (Y).......64.....61.....84.....70.....88.....92

    From this, you have estimated the regression equation using the least-squares method to be Ŷ = 33.5 + 1.7x. How well does this estimated equation fit the data?


    Any help would be great, these are the only questions Ive been stuck on going over past exam papers. Thanks folks.


Comments

  • #2
    cavedave
    Registered Users, Registered Users 2 Posts: 2,164 ✭✭✭cavedave


    4. When two variables are correlated, can you be sure that one variable causes the other? Why or why not?

    The size of cucmbers and the amount of suntan lotion bought are correlated. This does not mean that using suntan lotion causes cucumbers to grow large. Just that both events have a similar cause (sunshine).


  • #3
    Grudaire
    Registered Users, Registered Users 2 Posts: 3,620 ✭✭✭Grudaire


    Archimedes wrote: »
    1. When would you use the median rather than the mean as a measure of central tendency?

    If the mean is skewed by say one large number: eg mean v median of 5, 6, 7, 4, 3, 3, 100

    is median 5, mean 14ish
    Archimedes wrote: »
    2. "The Retail Price Index (RPI) is something of a compromise between a Laspeyres and a Paasche Index". Explain this statement.

    You what now?:confused:
    Archimedes wrote: »
    3. What do you understand by the term "statistically significant"?

    It means that you've found something worth talking about by using stats on the data:

    http://en.wikipedia.org/wiki/Statistical_significance

    Google it :D


  • #4
    Thomas_S_Hunterson
    Closed Accounts Posts: 6,151 ✭✭✭Thomas_S_Hunterson


    I'm guessing q5 involves getting the coefficient of determination (r-squared) to find out if it is a strong relationship. And possibly testing that the beta (slope) value for the relationship is not equal to zero.


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