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OpenStudy (jessicawade):

linear transformation model help

OpenStudy (jessicawade):

Number of months Number of fish 0 8 1 39 2 195 3 960 4 4,738 5 23,375

OpenStudy (jessicawade):

log y hat=0.9013x+0.6935

OpenStudy (jessicawade):

Use the linear transformation model to predict the number of fish in 12 months.

OpenStudy (jessicawade):

i got 5,685,367

OpenStudy (jessicawade):

@atreyu6s3x6

OpenStudy (anonymous):

haha sorry im bad at prob and stats

OpenStudy (mathmate):

The model is way off even at 5 months. Can you double-check the model?

OpenStudy (anonymous):

i think @mathmate has it haha

OpenStudy (jessicawade):

hmmm thats what i got

OpenStudy (jessicawade):

(log y hat=0.9013•logx+ 0.6935 ) this the other model thats is the closest to the one i have

OpenStudy (jessicawade):

but im pretty sure my log is correct

OpenStudy (jessicawade):

I have this question and the other one @atreyu6s3x6 tried helping me with. i can show you the entire part of the lesson if you need it.

OpenStudy (jessicawade):

Scientists are studying the population of a particular type of fish. The table below shows the data gathered over a five–month time period. Use the data to answer questions 5–9. Number of months Number of fish 0 8 1 39 2 195 3 960 4 4,738 5 23,375 5. What does the scatterplot of the data show? (1 point) • a strong positive linear relationship • a strong negative linear relationship • a curve that represents exponential growth * • a curve that represents exponential decay 6. Complete an exponential transformation on the y-values. What is the new value of y when x = 5? (1 point) • 4.3688 • 3.6756 * • 0.6990 • 3.3757 7. Find the linear transformation model. (1 point) • logy hat=o.6935•logx+ 0.9013 • log y hat=0.9013x+0.6935* • log y hat=0.6935x+ 0.9013 • log y hat=0.9013•logx+ 0.6935 8. Use the linear transformation model to predict the number of fish in 12 months. (2 points)

OpenStudy (jessicawade):

i put a * next to my answers

OpenStudy (mathmate):

It is much clearer when you post the complete original post. If you post your answer as part of the question, it will make the question inconsistent. First, do you think it is a linear or exponential relationship?

OpenStudy (jessicawade):

well i think its linear because when the x values increase so do the y values

OpenStudy (jessicawade):

JUST KIdding

OpenStudy (jessicawade):

its an exponential growth lol

OpenStudy (mathmate):

exactly! What have you learned about transformation?

OpenStudy (jessicawade):

not sure, i have taken notes but i lost the notebook earlier yesterday

OpenStudy (mathmate):

Do you have a textbook?

OpenStudy (jessicawade):

no im on online school

OpenStudy (mathmate):

You cannot go back to the lessons?

OpenStudy (jessicawade):

I can but they wont explain everything once i pass the lesson just bits

OpenStudy (jessicawade):

so i got log y hat=0.9013x+0.6935 as the transformation model out of the answers, but im not sure how to find the number of fish after 12 months, which is confusing me lol

OpenStudy (mathmate):

ok, are you looking for the answer or are you looking to understand?

OpenStudy (jessicawade):

understand please

OpenStudy (mathmate):

We'll rewind to the beginning, ok?

OpenStudy (jessicawade):

ok

OpenStudy (mathmate):

Typically, a linear model has the form y=ax+b but that's not our case.

OpenStudy (jessicawade):

ok

OpenStudy (mathmate):

Similarly, an exponential growth model has the form \(y=ax^{bx}\) where a and b are to be found.

OpenStudy (mathmate):

so far so good?

OpenStudy (jessicawade):

yes

OpenStudy (mathmate):

However, the parameters a and b are hard to calculate directly from the exponential model. Since we (including you) already know how to model a straight line, we will transform the exponential to a straight line. Then we'd find the parameters as though it is a straight line.|dw:1447097415267:dw| That's where transformation comes in.

OpenStudy (mathmate):

@jessicawade are you still there?

OpenStudy (jessicawade):

yeah my computer wasnt laoding

OpenStudy (jessicawade):

ohhhh ok :)

OpenStudy (mathmate):

The way the transformation works is you would take log (to base 10 in your case) on both sides. Can you do that for me?

OpenStudy (mathmate):

Take log on both sides of \(y=ax^{bx}\)

OpenStudy (jessicawade):

let me try im not very good at math

OpenStudy (jessicawade):

so on both sides on the y and the ax?

OpenStudy (jessicawade):

i dont get it xD

OpenStudy (jessicawade):

@mathmate

OpenStudy (mathmate):

\(y=ax^{bx}\) actually should read \(y=a(10)^{bx}\)........ if we take log 10 eventually We'll take log on both sides, so \(log(y)=log(ax^{bx})=log(a)+log(10^{bx})=log(a)+bx~log(10)=bx+log(a)\) This is done by the laws of logarithm (which you'll need to brush up for this course) Put it simply, \(log(y)=bx+log(a)\).........where a and b are constants to be found for the given data set.

OpenStudy (mathmate):

So we just finished the transformation part. Except for the laws of logarithm, are you following with the concept?

OpenStudy (jessicawade):

yeah so far i think haha

OpenStudy (mathmate):

It turns out that the constant "a" is the initial value, or the y-intercept.What is the y-intercept in our problem?

OpenStudy (jessicawade):

is that the same as log y?

OpenStudy (mathmate):

|dw:1447098799871:dw| "a", the y-intercept is the value of y when x=0. In our case, a=8 becase the number of fish is 8 at month 0.

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