AP Statistics 2017

For n ordered pairs (x, y ), we calculate: , , sx , sy , and r . Then we have:

example: For    the hours   studied (x  )   versus  score   (y  )   study,  the LSRL    is  ŷ = 59.03   +   6.77x   .   We

asked   earlier what    score   would   we  predict for someone who studied 2.75    hours.  Plugging    this

value   into    the LSRL,   we  have    ŷ = 59.03   +   6.77(2.75)  =   77.63.  It’s    important   to  understand  that

this    is  the predicted value,    not the exact   value   such    a   person  will    necessarily get.

example: Consider   once    again   the computer    printout    for the data    of  the preceding   example:

Exam    Tip: An AP  Exam    question    in  which   you are asked   to  determine   the regression  equation    from    the

printout    has been    common. Be  sure    you know    where   the intercept   and slope   of  the regression  line    are

located in  the printout    (they   are under   “Coef”).

The regression equation is given as “ = 59 + 6.77 Hours.” The y -intercept, which is the
predicted score when the number of hours studied is zero, and the slope of the regression line are listed in
the table under the column “Coef.”

example: We saw earlier that    the calculator  output  for these   data    was

The values  of  a and   b are   given   as  part    of  the output. Remember    that    these   values  were    obtained    by