We are sharing with you sample Interview questions for the post of Statistical Investigator
1.What are Mean, Mode, Median ?
- The Mean – To arrive at the mean of a set of numbers, you add the numbers up and then divide the sum by the number of numbers you were dealing with. (This is just like calculating what is called the “average.”) If your number set is 12, 8, 7, 15, and 7, for example, you would first add all those numbers together (equaling 49) and divide that sum by the number of numbers in your set (5). The result is 9.8. That’s your mean!
- The Median – This is the “middle” number in the set of numbers that you are dealing with. Think of it this way. Half of the numbers in the set are bigger than the median; half of the numbers are smaller. So to arrive at the median, simply put all the numbers in ascending order, with the smallest first. The number that is smack dab in the middle is the median. Aha you say, what if you have an even number of numbers in your set, not an odd number, so two numbers are in the middle? Well, the solution to that problem is easy; if that is the case, the median is midway between the two numbers that are in the middle of the set. So if your two middle two numbers are 7 and 9, your median is 8 (halfway in between).
- The Mode – Okay, this is pretty simple. The mode is the number in a set that appears most frequently. If you are dealing with those numbers we cited at the outset – 12, 8, 7, 15, and 7 – the mode is 7, because 7 appears twice, more than any other number. What if you have a set of numbers in which every number appears just once? Simple! You then have a set of numbers that doesn’t have a mode.
2.what is regression analysis ? Ans. In statistics, regression analysis is a statistical process for estimating the relationships among variables. It includes many techniques for modeling and analysing several variables, when the focus is on the relationship between a dependent variable and one or more independent variables. A statistical measure that attempts to determine the strength of the relationship between one dependent variable (usually denoted by Y) and a series of other changing variables (known as independent variables). 4.what is regression analysis ? In statistics, regression analysis is a statistical process for estimating the relationships among variables. It includes many techniques for modeling and analysing several variables, when the focus is on the relationship between a dependent variable and one or more independent variables. Surveys are a method of gathering information from individuals. Surveys have a variety of purposes, and can be conducted in many ways. Surveys may be conducted to gather information through a printed questionnaire, over the telephone, by mail, in person, by diskette, or on the web. This information is collected through use of standardized procedures so that every participant is asked the same questions in the same way. It involves asking people for information in some structured format. Depending on what is being analyzed, the participants being surveyed may be representing themselves, their employer, or some organization to which they belong. Typically, a questionnaire is a paper-and-pencil instrument that is administered to the respondents. The usual questions found in questionnaires are closed-ended questions, which are followed by response options. However, there are questionnaires that ask open-ended questions to explore the answers of the respondents.
- Advantages: Ideal for asking closed-ended questions; effective for market or consumer research
- Disadvantages: Limit the researcher’s understanding of the respondent’s answers; requires budget for reproduction of survey questionnaires
Between the two broad types of surveys, interviews are more personal and probing. Questionnaires do not provide the freedom to ask follow-up questions to explore the answers of the respondents, but interviews do.
- Advantages: Follow-up questions can be asked; provide better understanding of the answers of the respondents
- Disadvantages: Time-consuming; many target respondents have no public-listed phone numbers or no telephones at all
The probability of some observed outcomes given a set of parameter values is regarded as the likelihood of the set of parameter values given the observed outcomes. In statistical significance testing, the p-value is the probability of obtaining a test statistic at least as extreme as the one that was actually observed, assuming that the null hypothesis is true. If the p-value is less than 0.05 or 0.01, corresponding respectively to a 5% or 1% chance of rejecting the null hypothesis when it is true Sampling is that part of statistical practice concerned with the selection of an unbiased or random subset of individual observations within a population of individuals intended to yield some knowledge about the population of concern.
10.What are sampling methods? There are four sampling methods:
► Simple Random (purely random),
► Systematic( every kth member of population),
► Cluster (population divided into groups or clusters)
► Stratified (divided by exclusive groups or strata, sample from each group) samplings.
► first quartile (25th percentile)
► second quartile (50th percentile)
► third quartile (75th percentile)
► kth percentile
► prctile(x, 25) % 25th percentile, return 2.25
► prctile(x, 50) % 50th percentile, return 3, i.e. median
A hypothesis is a tentative statement about the relationship between two or more variables. A hypothesis is a specific, testable prediction about what you expect to happen in your study. For example, a study designed to look at the relationship between sleep deprivation and test performance might have a hypothesis that states, “This study is designed to assess the hypothesis that sleep deprived people will perform worse on a test than individuals who are not sleep deprived.”