qa-02

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course mth 173

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Question: `q001. Recall the stock value problem, where March, July and December values were $5000, $5300 and $5500.

Construct a graph of stock value vs. number of month (e.g., 1 for Jan, 2 for Feb, etc.). You will have three points on your graph, one corresponding to the March value, one to the July value, and one to the December value. Stock value will be on the y axis and month number on the x axis. Your first point, for example, will be (3, 5000), corresponding to $5000 in March.

Connect your three points with straight lines--i.e., connect the first point to the second and the second to the third.

What is the slope of your line between the first and second point, and what is the slope of your line between the second in the third point? Recall that slope is rise / run.

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Your solution:

To get the slopes as rise over run, we must take the coordinates and subtract them, then divide them.

So, from point 1 (3, 5000) to point 2 (7, 5300), we do 7-3 = 4, and 5300 - 5000 = 300.

Next we take 300/4 to get the slope. Which ends up being 75/1, or just 75.

For the slope of the second line segment, we take point 3 (12, 5500) and subtract point 2. So, 12 - 7 = 5 and 5500 - 5300 = 200.

200/5 is the slope, which ends up being 40/1, or just 40.

confidence rating #$&*:3

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Given Solution:

`aThe three points on the graph are (3, 5000), (7, 5300) and (12, 5500).

The rise between the first point and the second is from 5000 to 5300, or 300, and the run is from 3 to 7, or 4, so the slope is 300 / 4 = 75. Note that the 300 represents $300 and the 4 represents 4 months, so the slope represents $300 / (4 months) = $75 / month, which is the average rate of change during the first time interval.

The rise between the second point and the third is from 5300 to 5500, or 200, and the run from 7 to 12 is 5, so the slope is 200 / 5 = 40. This slope represents the $40/month average rate of change during the second time interval.

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Self-critique (if necessary):OK

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Self-critique Rating:OK

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Question: `q002. Look at your results for the slopes, and look the results for the average rates of change. What do you notice? In what way then does the graph represent the average rate of change?

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Your solution:

The graph accurately depicts the slopes, as the line segment from point 1 to point 2 is steeper than the line segment from point 2 to point 3. This shows how the average rate of change over the first time frame is greater than the average rate of change in the second time frame.

confidence rating #$&*:3

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Given Solution:

`aWe see from this example that the slope of a graph of value vs. clock time represents the rate at which value is changing with respect to clock time.

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Self-critique (if necessary):

My answer is a little more convoluted than the given solution, but it makes, basically, the same point, in that the graph is a visual representation of the average rate of change.

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Self-critique Rating:3

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Question: `q003. To what extent do you think your graph, consisting of 3 points with straight line segments between them, accurately depicts the detailed behavior of the stocks over the 9-month period?

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Your solution:

I think the graph is an accurate representation of how the stock did over a 9 month period, but it would be better if the data points were plotted more often. One point per month would be better than one every 4-5 months. It is better than day-to-day stats, as the market is often irrational in a day-to-day sense, so seeing the long term average is a much better visualization.

confidence rating #$&*:3

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Given Solution:

`aStocks can do just about anything from day to day-they can go up or down more in a single day than their net change in a month or even a year. So based on the values several months apart we can't say anything about what happens from day to day or even from month to month. We can only say that on the average, from one time to another, the stocks changed at a certain rate.

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Self-critique (if necessary):OK

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Self-critique Rating:OK

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Question: `q004. From the given information, do you think you can accurately infer the detailed behavior of the stock values over the nine-month period?

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Your solution:

Personally, I don’t think I could accurately infer details of the stocks based on the presented data, because the stock market can be so irrational at times. It is entirely possible that the stock was based on a company that makes most of its profits around the holidays, July 4th and Christmas, and thus had higher numbers at that time than it had in March. At best, with the given data it is only possible to assume that this is the average trend.

confidence rating #$&*:3

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Given Solution:

`aNot on a day-to-day basis, and not even on a month-to-month basis. All we can see from the given information is what might be an average trend.

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Self-critique (if necessary):OK

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Self-critique Rating:OK

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&#Good responses. Let me know if you have questions. &#