Accuracy & precision

background [prelab assignment (15 points) due at the begining of lab; reminder: as appropriate, use in-text citation & bibliography.

1. what's the difference between accuracy versus precision ?

2. what's the use of the below statistics tests ?

a. t-test versus 1-anova

b. F-test involving the variance

3. relate the below items.

a. variance & standard deviation

b. standard deviation, accuracy, & precision.

purpose

use of various devices to measure the volume of a liquid

compare the accuracy & precision of various laboratory equipment to measure the volume of a liquid

examine a histogram of your measurements

materials

electronic balance, weigh boat

10 mL pipet, modified 10 mL pipet, 10 mL graduated cylinder, 50 mL beaker, water - for 8.2 mL

100 mL graduated cylinder, 100 mL volumetric flask - for 100 mL

methods / data analysis: each group generates its own independent data, which is to be shared with the classs. 2 students / group.

methods

measure 8.2 (or 100) mL of water in the various volume measuring devices

measure its mass; record data

each student in the group obtains a data for each device,

if data is not described by the normal distribution, then each group, calculate the mean of your duplicate measurments - recall, prior lab about the central limit theorem

data analysis

student design; assume that the density of water is 1.0 g / mL and use it to determine the volume of water based on its mass and density, i.e. # mL = # g, since the density is 1.0 g / mL.

content of lab report [35 points; reminder: a pair of students may submit a lab report]

data [10 points]

histogram of your single measurements. describe the source of data in the histogram.

determine the mean and standard deviation for each measurement device

data analysis; justify / support your response; use statistics as appropriate; include a screen shot of the statistics test output and the type of statistics test used in your analysis. [20 points]

based on the histogram, does the data seem to be described by a normal distribution ? elaborate.

using the appropriate statistics test, . . . same ? different ? elaborate

what is the relative precision among the various equipment ?

what is the relative accuracy among the various equipment ?

is there a relationship between the relative accuracy versus relative precision in the various equipment. refer to data (and / or statistics) to support your response.

discussion [5 points]

in theory, there should be a difference in the relative precision in your data among the various equipment; rationalize. (hint: assume the mesurement devices are cylinders and refer to the formula for the volume of a cylinder; do not use calculus to solve the problem)

 

Resources

mathematica statistics

Excel - histogram (see section on "analysis tool pak")