Density Lab
Yes our true value fell within the confidence level. Both are within the confidence level, so we could conclude that our value is within the range for the true value.
Question 2
The confidence level increases with increasing % which is counter intuitive. The more confidence you have the "closer" the values should be. But if you think about it,
A broad question which can be answered in many different ways has a higher chance of being answered correctly than a more specific question with a smaller range of acceptable answers.
Question 3
If you use the beginning water level in your graduated cylinder for all three readings then each value would be off. If on the other hand you change the water for each of the volume readings, then you have a chance that the first incorrect value will only affect the first measurement. It won't help though if you still read the cylinder incorrectly. For our group, the first value was indepentent of the last two (we emptied the water and started fresh), but for the last two readings we just added more metal so an incorrect reading would carry through to the end.
1 comment:
1. Did the true value for density fall within the confidence interval? What is the significance of the confidence interval with respect your experimentally measured density and the true value of density?
2. Does the interval increase or decrease and as the confidence level changes from 90 to 95 to 99% and is the change intuitive? Could you explain the change to your students conceptually?
3. The procedure for measuring density for the liquid used a graphical approach as opposed to our three trials and average method for determining the density of the solid. If you made a determinant (human) error for your first measurement in the liquid density portion, would this error plague or affect the subsequent measurements? (try to think of a situation where it would not and a situation where it would).
Rita
1. Our metal was aluminum, with a density of 2.70 g/cm3. Our 95% confidence interval was 2.36 to 2.70 g/cm3, so the exact value was barely included. The confidence interval tells me that in 95% of like experiments, the density should be between 2.36 and 2.70 g/cm3.
2. As the confidence level increases, the confidence interval increases as well. This makes sense because if I want my value to be in the confidence interval, I need to have a bigger interval. I would tell my students that in order to have a bigger percentage of chance, you would have to have a bigger selection of numbers from which to choose.3. It would affect the outcome of the density. It would not necessarily affect the outcome of your other measurements. I would say that if I had a small number of experimental values, one wrong measurement would affect the outcome. If there were a large number of data values, one wrong value would not affect the outcome very much.
Smalley:
1. The value for our metal was within the confidence level, but somehow our values went askew and as a result, we received an answer that was closest to the density for aluminum instead of the copper we actually had. This is probably human error. For our water answer, however, we were spot on. The confidence level gives us some insight into the accuracy and precision of our lab data and subsequent calculations.
2. The confidence level increases as we increase the percentage of our confidence. This makes sense because as we increase the interval, we are increasing the certainty that the actual value is contained within this range. Yes. I would use the size of a target as an analogy.
3. Due to the procedure involved, any error will have a distorting effect on subsequent data points. An example where it would continue to effect would be if an instrument were mis-calibarated. A situation where the plague is eradicated would be the procedure is reset every single time a data point is collected (although new errors could be introduced).
Hascall:
1. Yes we were within the confidence level, but it didn't fit the known for our metal. Therefore there must have been human error. We need to look at the accuracy of our calculations.
2. The interval increases from 90% to 95%. When the range is smaller there is a smaller area for me to fall in and the 95% gives me a bigger area.
3. Yes, if you make the error on the original measurement then the resulting measurements will all be off. If you make the same error on every measurement then it should not affect the subsequent measurements.
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