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The purpose of the lab that was completed was to determine the validity and reliability of an electronic spirometer, using a water spirometer as a reference. Calibration is an important tool in determining whether or not an instrument is valid and reliable. The validity of an instrument is the extent to which a procedure accomplishes what it seeks out to accomplish. Validity can be determined by checking an instrument against another similar instrument.
From the tests run between the two instruments, Pearson's correlation coefficient (r) can be determined. This coefficient is a statistic that quantifies the magnitude of the relationship between two separate variables. The coefficient can range from negative 1 to positive 1. If the number is closer to positive one this means that when the variable increases, so does the other one. When the coefficient is closer to negative one this means when the variable increases, the other one does the opposite. Lastly, if the coefficient is closer to zero this means there is no relationship, positive or negative.
The coefficient r can be determined from the following equation: r = N (sum XY) (sumY) / N (sum x- (sum x) ) (N) (sum y- (sum y) ). The coefficient r can then be used to determine the shared variance between the two variables. Shared variance can be determined by the following equation: Shared Variance = r 100. If the shared variance is 75 % or better, this means there is a high correlation between the two variables. If the shared variance is between 50 - 75 %, this means there is a moderate correlation between the two variables.
Finally, if the shared variance is below 25 %, this means there is a low correlation. The reliability of a procedure is also very important. The reliability is the ability of an instrument or procedure to reproduce duplicate measurements. The reliability of a procedure is also calculated using Pearson's coefficient. It turns out that the reliability coefficient is usually higher than the validity coefficient, since with the reliability test you are not comparing two different procedures or instruments, but the same one; and one would expect that if a procedure was repeated using the exact same instruments then the results would be very similar.
Before any instruments were tested the humidity, barometric pressure, and temperature were recorded. The PH 2 O was determined by using the table included in the lab notebook. The subjects were asked to measure their forced vital capacity using both an electronic spirometer and a water spirometer. The water spirometer was filled with water and calibrated.
Once this was accomplished, each subject inspired a full breath of air and expired it through a mouthpiece on the spirometer while holding their nose. This was done 3 times per subject and the highest value was then recorded and then corrected using the BTPS factor, since this spirometer did not account for the correction. The subjects were then asked to use the electronic spirometer to determine their vital capacity. Taking a full breath and expelling it out into the mouthpiece did this. The digital readout was then recorded. Three trials were done on the electronic spirometer and the highest value was recorded.
The value was recorded without the correction factor since the device took the correction factor into account. After the first three trials were performed, three more trials were performed and the highest value was recorded again. From the obtained values, reliability and validity could be determined. The electronic spirometer that was provided was called a micro medical vacuumed spirometer.
The water spirometer was called a Collins vitalometer water spirometer. The purpose of the experiment was to determine the validity and reliability of the electronic spirometer when comparing it to the water spirometer. The validity of the electronic spirometer proved to show a very high correlation between the results of the electronic and water spirometer. Using the excel spreadsheet, the validity coefficient was determined to be. 8363 and the shared variance was 70. 02 %. What this means is that the results were very similar between the electronic and water spirometer. This implies that the electronic spirometer is a valid instrument when compared to the proven water spirometer.
Pearson's r was also found for the second trial and the water spirometer and the results were r = . 8275. This means that the shared variance was 68. 4 %. This shows a moderate correlation. The reliability was also determined, and Pearson's r = . 9804. Which means the shared variance is 96. 1 %. This is a very high correlation, probably because it is easier for an instrument to be reliable than valid.
Thomas, J. R. and Nelson, J. K. (1990). Research methods in physical activity.
Champaign IL: Human Kinetics Book, pp 343 - 363
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Research essay sample on Trials Were Performed Highest Value Was Recorded Spirometer
