document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=132363>Question 132363</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please help me.  I need answer to this question desperately. Please kindly help me.\r<BR>\n" );
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document.write( "a) Plot the data on U.S. general aviation shipments. (b) Describe the pattern and discuss possible causes. (c) Would a fitted trend be helpful? Explain. (d) Make a similar graph for 1992–2003 only.  Would a fitted trend be helpful in making a prediction for 2004? (e) Fit a trend model of your choice to the 1992–2003 data. (f) Make a forecast for 2004, using either the fitted trend model or a judgment forecast. Why is it best to ignore earlier years in this data set? Airplanes<BR>\n" );
document.write( "U.S. Manufactured General Aviation Shipments, 1966–2003<BR>\n" );
document.write( "Year	Planes<BR>\n" );
document.write( "1966	15,587<BR>\n" );
document.write( "1967	13,484<BR>\n" );
document.write( "1968	13,556<BR>\n" );
document.write( "1969	12,407<BR>\n" );
document.write( "1970	7,277<BR>\n" );
document.write( "1971	7,346<BR>\n" );
document.write( "1972	9,774<BR>\n" );
document.write( "1973	13,646<BR>\n" );
document.write( "1974	14,166<BR>\n" );
document.write( "1975	14,056<BR>\n" );
document.write( "1976	15,451<BR>\n" );
document.write( "1977	16,904<BR>\n" );
document.write( "1978	17,811<BR>\n" );
document.write( "1979	17,048<BR>\n" );
document.write( "1980	11,877<BR>\n" );
document.write( "1981	9,457<BR>\n" );
document.write( "1982	4,266<BR>\n" );
document.write( "1983	2,691<BR>\n" );
document.write( "1984	2,431<BR>\n" );
document.write( "1985	2,029<BR>\n" );
document.write( "1986	1,495<BR>\n" );
document.write( "1987	1,085<BR>\n" );
document.write( "1988	1,143<BR>\n" );
document.write( "1989	1,535<BR>\n" );
document.write( "1990	1,134<BR>\n" );
document.write( "1991	1,021<BR>\n" );
document.write( "1992	856<BR>\n" );
document.write( "1993	870<BR>\n" );
document.write( "1994	881<BR>\n" );
document.write( "1995	1,028<BR>\n" );
document.write( "1996	1,053<BR>\n" );
document.write( "1997	1,482<BR>\n" );
document.write( "1998	2,115<BR>\n" );
document.write( "1999	2,421<BR>\n" );
document.write( "2000	2,714<BR>\n" );
document.write( "2001	2,538<BR>\n" );
document.write( "2002	2,169<BR>\n" );
document.write( "2003	2,090\r<BR>\n" );
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document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #96720 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=96720\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a) Plot the data on U.S. general aviation shipments.<BR>\n" );
document.write( "You can do that with a dot-plot.<BR>\n" );
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document.write( "(b) Describe the pattern and discuss possible causes.<BR>\n" );
document.write( "There is a definite downward trend in number of shipments.<BR>\n" );
document.write( "Possible causes are: price of gasoline to the buyer; price of insurance<BR>\n" );
document.write( "due to terroism.<BR>\n" );
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document.write( "(c) Would a fitted trend be helpful? Explain.<BR>\n" );
document.write( "While there is a consistent downward trend the quantitative<BR>\n" );
document.write( "changes are not consistent.  A fitted trend would not be helpful.<BR>\n" );
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document.write( " (d) Make a similar graph for 1992–2003 only. Would a fitted trend be helpful in making a prediction for 2004?<BR>\n" );
document.write( "1992 856<BR>\n" );
document.write( "1993 870<BR>\n" );
document.write( "1994 881<BR>\n" );
document.write( "1995 1,028<BR>\n" );
document.write( "1996 1,053<BR>\n" );
document.write( "1997 1,482<BR>\n" );
document.write( "1998 2,115<BR>\n" );
document.write( "1999 2,421<BR>\n" );
document.write( "2000 2,714<BR>\n" );
document.write( "2001 2,538<BR>\n" );
document.write( "2002 2,169<BR>\n" );
document.write( "2003 2,090 <BR>\n" );
document.write( "It appears that 2004 should have close to 2000 shipments.<BR>\n" );
document.write( "A fitted trend might  be helpful as the pattern is gradually <BR>\n" );
document.write( "up to a max at year 2000, then down.<BR>\n" );
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document.write( " (e) Fit a trend model of your choice to the 1992–2003 data.<BR>\n" );
document.write( "Using a Quadratic Regression function on a TI calculator I get:<BR>\n" );
document.write( "y = -12.195..x^2+357.867x -167.92<BR>\n" );
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document.write( " (f) Make a forecast for 2004, using either the fitted trend model or a judgment forecast.<BR>\n" );
document.write( "Using the trend model I get: 2452<BR>\n" );
document.write( "Using judgment forecast: I think 2000<BR>\n" );
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document.write( " Why is it best to ignore earlier years in this data set?<BR>\n" );
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document.write( "I'll leave that to you.<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.\r<BR>\n" );
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document.write( " Airplanes U.S. Manufactured General Aviation Shipments, 1966–2003<BR>\n" );
document.write( "Year Planes<BR>\n" );
document.write( "1966 15,587<BR>\n" );
document.write( "1967 13,484<BR>\n" );
document.write( "1968 13,556<BR>\n" );
document.write( "1969 12,407<BR>\n" );
document.write( "1970 7,277<BR>\n" );
document.write( "1971 7,346<BR>\n" );
document.write( "1972 9,774<BR>\n" );
document.write( "1973 13,646<BR>\n" );
document.write( "1974 14,166<BR>\n" );
document.write( "1975 14,056<BR>\n" );
document.write( "1976 15,451<BR>\n" );
document.write( "1977 16,904<BR>\n" );
document.write( "1978 17,811<BR>\n" );
document.write( "1979 17,048<BR>\n" );
document.write( "1980 11,877<BR>\n" );
document.write( "1981 9,457<BR>\n" );
document.write( "1982 4,266<BR>\n" );
document.write( "1983 2,691<BR>\n" );
document.write( "1984 2,431<BR>\n" );
document.write( "1985 2,029<BR>\n" );
document.write( "1986 1,495<BR>\n" );
document.write( "1987 1,085<BR>\n" );
document.write( "1988 1,143<BR>\n" );
document.write( "1989 1,535<BR>\n" );
document.write( "1990 1,134<BR>\n" );
document.write( "1991 1,021<BR>\n" );
document.write( "1992 856<BR>\n" );
document.write( "1993 870<BR>\n" );
document.write( "1994 881<BR>\n" );
document.write( "1995 1,028<BR>\n" );
document.write( "1996 1,053<BR>\n" );
document.write( "1997 1,482<BR>\n" );
document.write( "1998 2,115<BR>\n" );
document.write( "1999 2,421<BR>\n" );
document.write( "2000 2,714<BR>\n" );
document.write( "2001 2,538<BR>\n" );
document.write( "2002 2,169<BR>\n" );
document.write( "2003 2,090 \r<BR>\n" );
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document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );