Basic sampling issues
14 important questions on Basic sampling issues
Is it true that a census provides more accurate results than a sample?
No not necessarily true, there are many impediments to actually obtaining information from every member of the population, so the ideal census is seldom attainable.
How to specify a population of interest?
In terms of geographic area, demographics, product usage characteristics, awareness measures.
Also include security questions to exclude people from the survey.
Is there often a perfect correspondence between the sampling frame and the population of interest?
No, seldom, because the list of populaton members is often not complete and accurate.
- Higher grades + faster learning
- Never study anything twice
- 100% sure, 100% understanding
For my 1st exam I got a C. Then, I started looking for ways to learn better and I came across Study Smart. Since then I have scored a A+, A, A- and another A. I highly recommend it to everyone who wants to hear it. I am so happy with it!!
I was struggling to finish all my first-year subjects for 3 years. Then I discovered Study Smart, which helped me to finish all of them within 3 months.
Because of StudySmart, things are going well in many ways. Before, I always had study stress and no time for anything. Now I feel calm and confident (because of the program). I used to score a B, now I usually score an A or A+.
Hey Chris, I really want to thank you very much for developing the platform, I usually got around C for my exams, now I scored an A+, an A and a A- !!
Since using Study Smart, my average has increased significantly. I even completed a statistics course with a A+ while I'm bad at statistics. I took on extra courses this year, because of Study Smart. Thanks so much!
Ever since I started studying with StudySmart I passed all my exams !!! No more re-sits!! At first, I was happy with a pass and now I only get good grades. Many thanks!
I aced all the courses I studied with Study Smart. For law, I first scored a D, and now an A! I’m 100% sure that I’ll pass all the courses I study with Study Smart.
I always thought I studied well. My grades were fine. I could never have imagined that applying these study skills would have such a huge and direct impact on my grades, my speed and the pleasure I have in learning.
For the first time, I finally feel totally confident about the way I learn. I have the perfect overview and make great progress in terms of speed and the grades I get. Thanks, Chris!
I immediately started to enjoy learning again, and my grades soared. All of a sudden, everything went better. I highly recommend Study Smart to all students..
Being able to create my materials online made the process of studying so much smoother and quicker. I no longer have to spend a huge amount of my time on creating my summaries.
At first, my notes were a mess. Now I use Study Smart to take my notes in a perfectly structured way. It helps me to save a lot of time and do other things I enjoy.
Students that study with Study Smart get better grades. The system applies all the learning methods in such a way that both well-performing students and students who struggle perform much better.
Hi Chris, I would like to thank you very much. Last year I scored C on a course, and this year I got an A+ thanks to your method! Thank you very much!
The largest effect is that my child is more enthusiastic about school! Every parent wants their children to be happy at school, Study Smart made it happen.
In high school, I failed several exams, and that has really changed now. I actually needed this tool very much back then. Since I started studying with StudySmart, I haven't had any D's. My average score is now an A and those are results I would have never had in the past
With my old method, I passed only 3 out of 8 courses. Since I started taking my notes digitally in Study Smart, I have passed all my courses on the first try. For me, StudySmart takes away the stress of wondering if I will pass or not.
Thanks to StudySmart, I passed all my exams, and with better grades than before! On top of that, I have mastered a very good study method now, which I am confident will help me earn my degree.
Two types of sampling methods
- Probability sampling: every element of the population has a known nonzero likelihood of selection.
- Nonprobability sampling: samples in which specific elements from the population have been selected in a non-random manner.
Disadvantages of probability sampling over nonprobability sampling
- Usually more expensive
- Rules for selection increase interviewing costs and professional time spent in designing and executing the sample design.
How to determine the sample size for a nonprobability sample
Rely on factors such as available budget, rule of thumb and number of subgroups to be analyzed.
How to determine the sample size for a probability sample
Use formuleas to calculate the sample size required, given the target levels of acceptable error (difference between sample result and population value) and levels of confidence (likelihood the confidence interval will include the population value).
Accuracy of sample results is affected by two types of error
- Sampling error
- Measurement error
When is there no difference between disproportional and proportional allocation?
When the distributions of the characteristics under consideration (stratums) have the same standard deviation.
Difference of cluster sampling and stratified sampling
Stratified sampling: select elements from each subgroup (stratum).
Cluster sampling: select all elements in the subgroup (one stage) or from a sample of the elements in the subgroup (two-stage).
Cluster samples have ... cost efficiency and ... statistical efficiency
Greater cost efficiency. Lower statistical efficiency due to larger sampling error than simple random sample or stratified sample of the same size.
Two key differences between quota samples and stratified samples
- Respondents for stratified samples are selected randomly, for quota samples they are not.
- Classification factors used for stratified samples are selected based on the existence of a correlation between the factor and the behaviour of interest.
Advantages of internet interviewing
Target respondents can complete the survey at their own convenience
Data collection is relatively inexpensive
Interview can be administered under software control
Survey can be completed quickly
Disadvantage of internet interviewing
People in cyberspace do not correctly represent the general population, as they tend to be more whith, richer, male and tech savvy.
The question on the page originate from the summary of the following study material:
- A unique study and practice tool
- Never study anything twice again
- Get the grades you hope for
- 100% sure, 100% understanding
