Reducing Sample Size Once the sample has been made homogeneous, a small more manageable portion is selected for analysis. Later, when the project was resumed, I filled in the blank with the number of the page on which I recorded the very next set of information. Label the axes on a graph, being sure to include units of measurement. Sources of Error There are three common sources of error in any analytical technique: · Personal Errors Blunders. This is also where you would discuss any mistakes you might have made while conducting the investigation. The diameter of each of the 5 objects was measured with either the ruler or caliper.
Rejecting Data When carrying out an experimental analytical procedure it will sometimes be observed that one of the measured values is very different from all of the other values, e. After you have described what happened in each experiment, you can begin discussing what can be learned from the data. I didn't simply go outside and sun myself every time I had a one hour wait during a protocol. Lab Analysis Questions 5 points each 1. If C is proportional to D, we should get a straight line through the origin. Most of the subsequent chapters deal with the description of various analytical procedures developed to provide information about food properties, whereas this chapter focuses on the other aspects of food analysis. · A population may be either homogenous or heterogeneous.
The circumference measurement was obtained by tightly wrapping a small piece of paper around the object, marking the circumference on the paper with a pencil, and measuring this distance with the ruler or caliper. We measured the circumference and diameter of five circular objects ranging from 2 cm to 7 cm in diameter. In high-intensity sampling years, several additional high-flow samples were collected to characterize that part of the hydrograph where concentrations might be more variable. Consequently, the sampling plan has to be much more rigorous for detection of potentially harmful substances than for quantification of quality parameters. Many foods contain active enzymes they can cause changes in the properties of the food prior to analysis, e. Make sure you interpret the meaning of both the slope and intercept. Lab Analysis Questions 5 points each 1.
Record your data in Chart 1. Just don't hide any of your entries. A sampling plan should be a clearly written document that contains precise details that an analyst uses to decide the sample size, the locations from which the sample should be selected, the method used to collect the sample, and the method used to preserve them prior to analysis. It is typically the highest alcohol content achieved before adjusting to the level needed for bottling. The primary objective of sample selection is to ensure that the properties of the laboratory sample are representative of the properties of the population, otherwise erroneous results will be obtained. The sample may be comprised of one or more sub-samples selected from different regions within the population.
Graphs are especially useful for examining possible trends over the range of measurements. Even if you don't write a whole introduction, you need to state the purpose of the experiment, or why you did it. Use the data chart to answer the following questions. What are the important ions for most neurons when considering changes in membrane potential? Freezing, drying, heat treatment and chemical preservatives or a combination are often used to control enzyme activity, with the method used depending on the type of food being analyzed and the purpose of the analysis. Microorganisms are present naturally in many foods and if they are not controlled they can alter the composition of the sample to be analyzed. It does not necessarily have to correspond to the true value of the parameter one is trying to measure.
Thus if any problem arises, it can easily be identified. Alternatively, the person who selects the sub-samples may have some experience about where the worst sub-samples are usually found, e. · Microbial Growth and Contamination. If an analysis is not shown in a particular package,this does not imply that the package cannot do the analysis, it may simply mean that the analysis is not commonly done in that package by our clients. The the one you are measuring is on the Y-axis. Measure of Spread of Data The spread of the data is a measurement of how closely together repeated measurements are to each other. You simply read each passage and follow the continuation notes to follow a single project from start to finish.
. Describe purpose and benefits of organising data so that it can be analysed. Random sampling is often preferred because it avoids human bias in selecting samples and because it facilitates the application of statistics. The use of paper to measure the circumference was probably the most significant source of uncertainty. On the other hand, a variable is some property that can be measured on a continuous scale, such as the weight, fat content or moisture content of a material.
Selection of an appropriate fraction of the whole material is one of the most important stages of food analysis procedures, and can lead to large errors when not carried out correctly. Be sure to refer to figures and graphs in the text of your report. Many analytical techniques destroy the food and so there would be nothing left to sell if it were all analyzed. Each sample should be marked with a code on its label that can be correlated to the notebook. Look at the experimental evidence collected and talk about why you think you got these results.
Which intensity of which modality created the greatest amplitude of response? Start every experiment with a title and a brief introduction. Sometimes an introduction may contain background information, briefly summarize how the experiment was performed, state the findings of the experiment, and list the conclusions of the investigation. There are a number of ways these changes can be prevented. Record contents in chronological order. An officially sanctioned sampling plan and analytical protocol is often required for this type of analysis.
Most modern calculators and spreadsheet programs have routines that can be used to automatically determine the regression coefficient, the slope and the intercept of a set of data. Exposure to light, elevated temperatures, oxygen or pro-oxidants can increase the rate at which these reactions proceed. It is typically the highest alcohol content achieved before adjusting to the level needed for bottling. Conversely, if a student did not contribute to the writing or analysis of the lab their name should not appear on the title page or in the title section. A series of calibration experiments is carried out using samples with known properties and a standard curve is plotted from this data.