In the E6 experiment, the molar mass of an unknown gas was worked out using measurements from two different experiments. The data was collected by around 450 students during the week, providing a large data set. In this experiment, the value of the molar mass is actually known but it serves as a very useful model for analysing the reliability, precision and accuracy of experimental data. The purpose of this task is for you to use spreadsheet software to perform a quantitative analysis of the data to assess these factors.

Although applied here to what may seem an abstract problem in physical science, the skills that you will develop are used across the physical, natural and applied sciences and in business to analyse the reliability and meaning of data.

The physical sciences are often portrayed as being concerned with "facts". The measurements obtained in this experiment were all obtained on the same gas, using apparently identical equipment and techniques. It should become clear that all measurements are actually susceptible to a wide range of influences, including human error, instrument failure and inadequacies in the design of the experiment. Data recorded in a book or on a computer can be typed in incorrectly, probably accidently but perhaps also maliciously. The professional scientist must be aware of these limits of experiment and report results that do not exceed the precision and accuracy of the experiment. This is clearly important for sciences, like chemistry, that have evolved through experimental observations. For the life sciences, the accuracy and reliability of the data may have more immediate consequences.

Assessment Details and Hand-In Dates This task represents 2% of your unit mark and 2/15 of the laboratory mark. The completed task must be handed to your demonstrator during your class in week 6 or week 7. Work handed in a week late will attract a maximum mark of 1%. Later submission will result in a zero. When you hand your report to your demonstrator, you must sign and date their record sheet.

The data you are going to analyse is that obtained by experimentalists (i.e. you and your peers). Depending on the results obtained, it may be very precise and very accurate or neither of these things. There are no marks associated with the quality of your results or those of the class. The marks are awarded for the quality of the analysis:

clear graph with appropriately chosen ranges on the axes, suitable labels for the data and x and y-axes and a clear title which summarizes the content of the figure (1/2 mark)

calculation of the averages and standard deviations for the data obtained from both experiments and correctly reported result including standard error (1/2 mark)

discussion of the accuracy and precision of each experimental method and comparison of these methods (1/2 mark)

use of Chauvenot’s criterion for suspected outlier and assessment of whether point should be removed (1/2 mark)

The task develops a number of important generic and professional attributes, including Faculty of Science graduate attributes:

use a range of computer software packages in the process of gathering, processing and disseminating scientific knowledge

make value judgements about the reliability and relevance of information in a scientific context

appreciate the roles of accuracy and precision in the reporting of scientific information, and the difference between these concepts

The task will develop a number of specific skills, important for scientific research and graduate level employment:

use of computer spreadsheets for data analysis and for the presentation of data, using MS Excel

calculation of standard deviation

use of statistical tests as indicators of data reliability and for detection of outliers

The task also asks you to self assess your work. You are given the marking scheme and have to assess how you work meets the criteria. Being able to accurately and honestly self assess your progress (and hence identify) your weaknesses is extremely important. It marks an acceptance of your role and responsibility in your learning and a break from your reliance on the teacher, as summarized in the graduate attribute:

evaluate your own performance and development, to recognize gaps in knowledge and acquire new knowledge independently

The experimental data is available as a .csv file which should open in any spreadsheet program, including the various version of MS Excel and Sun OpenOffice. The task instructions are tailored for Excel as this is the most commonly used spreadsheet program in education, commerce and business. If you are using another spreadsheet program, you should use these instructions alongside the manual/help pages for that application.

To get started download, the experimental database and the instructions. Complete the assignment using the template. Print it out and bring it to your demonstrator.

Assessment Details and Hand-In Dates This task represents 2% of your unit mark and 2/15 of the laboratory mark. The completed task must be handed to your demonstrator during your class in week 6 or week 7. Work handed in a week late will attract a maximum mark of 1%. Later submission will result in a zero. When you hand your report to your demonstrator, you must sign and date their record sheet. Downloads Database of measurements Task instructions Report template in Word 2007, Word 2003 and PDF formats W6 Data Analysis 1 (also available in the 'Laboratory Handbook') W7 Data Analysis 1 (also available in the 'Laboratory Handbook')