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Problem 105
How would you check whether data points of the form $\left(1, y_{1}\right),\left(2, y_{2}\right),\left(3, y_{3}\right)$ lie on an exponential curve?
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Why is the logarithm of a negative number not defined?
What happens to the function \(P(t)=\frac{N}{1+A b^{-t}}\) if \(A=0 ?\) If
Use technology to find a logistic regression curve \(y=\frac{N}{1+A b^{-x}}\) approximating the given data. Draw a graph showing the data points and regression curve. (Roumd \(b\) to three significant digits and \(A\) and \(N\) to two significant digits.) $$ \begin{array}{|l|c|c|c|c|c|c|} \hline \boldsymbol{x} & 0 & 30 & 60 & 90 & 120 & 150 \\ \hline \boldsymbol{y} & 2.8 & 5.8 & 7.9 & 9.4 & 9.7 & 9.9 \\ \hline \end{array} $$
New York \mathrm{\\{} C i t y ~ H o u s i n g ~ C o s t s : ~ D o w n t o w n ~ T h e ~ f o l l o w i n g ~ table shows the average price of a two-bedroom apartment in downtown New York City during the real estate boom from 1994 to \(2004 .^{24}\) $$ \begin{array}{|c|c|c|c|c|c|c|} \hline \boldsymbol{t} & 0(1994) & 2 & 4 & 6 & 8 & 10(2004) \\ \hline \begin{array}{r} \text { Price } \\ \text { (S million) } \end{array} & 0.38 & 0.40 & 0.60 & 0.95 & 1.20 & 1.60 \\ \hline \end{array} $$ a. Use exponential regression to model the price \(P(t)\) as a function of time \(t\) since 1994 . Include a sketch of the points and the regression curve. (Round the coefficients to 3 decimal places.) HINT [See Example 6.] b. Extrapolate your model to estimate the cost of a twobedroom downtown apartment in 2005 .
Epidemics There are currently 1,000 cases of Venusian flu in a total susceptible population of 10,000 and the number of cases is increasing by $25 \%$ each day. Find a logistic model for the number of cases of Venusian flu and use your model to predict the number of flu cases a week from now. HIIIT [Example 1.]
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