Jimyeong Park

Data Management

28 April 2013.

CH 2.2 Indices -it is an index relates the value of a variable to base level, which is value particular date. In this case, Index produces numbers are easy to understand and compare. Also, it’s compare different time have different price and production, like CPI(consumer price Index), use different year to compare one place different CPI. So we can see graph that shows how a variable changes over time. The consumer price index (CPI) is the most widely reported of these economic indices because it is an important measure of inflation. Inflation is a general increase in prices, which corresponds to a decrease in the value of money. To measure the average change in retail prices across Canada, Statistics Canada monitors the retail prices of a set of over 600 goods and services including food, shelter, clothing, transportation, household items, health and personal care, recreation and education, and alcohol and tobacco products. Also we need a Time-series graphs, it can be often used to show how indices change over time. Such graphs plot variable values versus time and join the adjacent data points with straight lines. Statistics Canada calculates a variety of carefully researched economic indices. The consumer price index (CPI) tracks the overall price of a representative basket of goods and services, making it a useful measure of inflation.

CH2.3 Sampling Techniques Sampling techniques is a shortcut method for investigating a whole population. Data is gathered on a small part of the whole parent population or sampling frame, and used to inform what the whole picture is like. The group of individuals who actually have a chance of being selected is called the sampling frame. The sampling frame varies depending on the sampling technique used. Here are some of the most commonly used sampling techniques. Sampling techniques has three main types of sampling strategy: Random、Systematic and Stratified. Random sampling is the purest form of probability sampling. Each member of the population has an equal and known chance of being selected. When there are very large populations, it is often difficult or impossible to identify every member of the population, so the pool of available subjects becomes biased. Advantages and disadvantages of random sampling. Advantages: Can be used with large sample populations and avoids bias. Disadvantages: Can lead to poor representation of the overall parent population or area if large areas are not hit by the random numbers generated. This is made worse if the study area is very large. There may be practical constraints in terms of time available and access to certain parts of the study area.

Systematic sampling is often used instead of random sampling. It is also called an Nth name selection technique. After the required sample size has been calculated, every Nth record is selected from a list of population members. As long as the list does not contain any hidden order, this sampling method is as good as the random sampling method. Its only advantage over the random sampling technique is simplicity. Systematic sampling is frequently used to select a specified number of records from a computer file.

Stratified sampling is commonly used probability method that is superior to random sampling because it reduces sampling error. A stratum is a subset of the population that shares at least one common characteristic. Examples of stratums might be males and females, or managers and non-managers. The researcher first identifies the relevant stratums and their actual representation in the population. Random sampling is then used to select a sufficient number of subjects from each stratum. "Sufficient" refers to a sample size large enough for us to be reasonably confident that the stratum represents the population. Stratified sampling is often used when one or more of the stratums in the population have a low…