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Biology Lab Analysis
1a. Our data shows the 125mL Erlenmeyer flask as having the lowest Percent Error of
Mean (0.45%), meaning that this should be the most accurate measuring device. This is
false in most cases, though, because the 100mL graduated cylinder should be the most
accurate device because it is more calibrated, in other words, it has more measuring ticks.
1b. From the data collected in Section 1.3, one cannot easily determine the precision
because measurements were only taken three times, and precision is the consistency a
number is reproduced. We would need to do more trials and calculate the standard
deviation of the mean to determine the precision. The smallest number calculated from
the standard deviation would be the most precise.
2a.
•
The class data has a mean closer to the target value of 9mL. Our group mean was
8.48mL and the class data was 8.68mL.
•
The percent error of the mean indicates accuracy.
•
The class data is more accurate because its percent of the mean is 0.04% and our
group was 0.06%. The smaller percentage indicates that it deviates less from the
target value.
•
The statistic indicating precision is standard deviation.
•
Our group data is more precise because we have a smaller standard deviation. We
used the same balance for all measurements, which could indicate why all of them
were similar, even though with larger sample sizes, there are more chances the
samples have to be the average value.
2b.
•
The percent error is less for the 10mL glass Blowout pipet, so this device is
more accurate. The pipet is skinnier and the calibrations are further apart so it is
easier to see that the bottom of the meniscus is touching the correct measurement
line. Also, the amount of water being taken into the pipet can be controlled, rather
than poured in.
•
The cylinder has a lower standard deviation, meaning that it is more precise. The
reason for this could be because the blow out pipet is a relatively new device for
many students, so some may have bubbles form in their pipet, whereas the
graduated cylinder is easy to obtain the same measurement because its an easier
process; water is poured inside.
3. (attached)
4a. The assumed null hypothesis is that these two sets of data are the same for both the
cylinder and the pipet because it’s the same 9mL measurement.
4b. The group data mean was 8.48 +/ 0.08mL for the 10mL graduated cylinder. The
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View Full Document group data mean was 9.38 +/ 0.66mL for the 10mL glass Blowout pipet. Pvalue was
0.1388
The class data mean was 8.62 +/ 0.12mL for the 10mL graduated cylinder. The class
data mean was 8.95 +/ 0.33mL for the glass Blowout pipet. Pvalue was .00081314
4c. Group data: No, meaning the null hypothesis is not rejected and the two sets of data
are not statistically different. They could be similar by chance because the sample size is
so small, so there were less chances for differing measurements. Also, the same balance
was used, whereas, in a larger sample size with different balances, as in the class data, the
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This note was uploaded on 01/30/2012 for the course BIO 205L taught by Professor Hanson during the Fall '07 term at University of Texas at Austin.
 Fall '07
 Hanson
 Biology, molecular biology

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