Lab Report for Experimental Errors Lab

Part I. Calibration of your mL pipette.

First fill out the printed report form. Then fill in this form. Note that this form asks for slightly different data from that of the report form.

Sample calculation for 1st volume determination:

Data:

Temperature of water: °C.

weighings: (Double-clicking in a flask+cork cell will copy previous flask + cork + water result)

	Mass of flask + cork (g)	Mass of flask + cork + water from pipet (g)	Didn't use data (explain below)
1.
2.
3.
4.
5.
6.
(7.)
(8.)

If you checked any boxes above, explain why these data were rejected from averaging:

Calculations:

Apparent density of water: g / mL

Volume delivered by pipette. Enter results here using at least 3 decimal places (to the nearest microliter):

Mean = mL

Standard deviation (s) = mL

Express your results using significant figure rules discussed in the lab manual:

The volume delivered by the pipette is

+/- mL.

Express the accuracy of the pipette (or lack thereof) as a % error (equation 3): Error = %

Part 1 Error Checking (click on this box to see if errors are detected):

Part II. Accuracy of various methods of measuring mL.

Fill in the following table of volumes, with your data on the first line. For your data, show a sample calculation for the actual volume delivered by the buret, starting from mass readings of the flask before and after adding water from the buret::

Use data from at least three of your classmates (for at total of at least four volumes per column). If you decide to neglect a value from your calculations, just leave the space blank in the table, but explain here (including what the value was and why you rejected it).

All volumes should be entered in units of mL (no need to enter mL for each entry). Use sig fig rules described in text for mean +/- std. dev.

Name of experimentalist who provided data:	A: Erlenmeyer flask contains	B: mL volumetric flask contains	C: mL volumetric flask delivers	D: 50 mL buret	E: mL pipette	F: 100 mL grad. cyllinder	G: 10 mL grad. cyllinder
Your data in top row:






mean values:
+/- s:
Percent Error
Calculation check:*

* - For some columns, the calculational check icon is updated every time you enter a value; for others you must roll your mouse pointer over the (yellow) icon to check the calculations. The checker requires at least four non-blank values for volumes, and requires that the mean value and +/- s be expressed using the significant figure rules for such expressions (one sig fig for s and the same number of decimal places for the mean value).

Rank ordering of precision and accuracy. Rank the methods for precision and accuracy, based on the experimental mean and standard deviations. (include also your hypothesis).

	hypothesis (precision & accuracy)	experimental precision	experimental accuracy
most:





least:

Answers to Questions:

Question 1: Is the mean volume delivered by your mL pipette significantly different from the marked volume of.00 mL? Use a 95% confidence criterion (+/- 2s) for significance, and briefly explain your answer.

Question 2: Were the most precise methods of measurement of mL also the most accurate methods? Comment briefly about whether the results were as you predicted, or if you were surprised.

Question 3: What was the least precise method of measurement of mL? Was this what you predicted beforehand? Comment on why this method has low precision (low precision means high standard deviation).

Please enter your Haverford email username and password information before submitting this form.*

Username: @ Password:

* - On some browsers/systems, hitting Enter or Return is equivalent to clicking the Submit button. To prevent accidentally submitting information before you have finished filling in or checking this form, I recommend that you don't fill your password in until you are ready to submit. Your username, but not your password, will be recorded along with all your form entries in the database of lab report submissions.

You are encouraged to use the error-checking buttons and icons to find errors before submitting your lab report. The error-checking buttons and fields on this form are designed to help you avoid errors, but are not programmed to look for all errors, and in addition may miss some errors. If you believe an error-checker is not working correctly, you may submit anyway.

Form created by Rob Scarrow. rscarrow@haverford.edu