Randomization Notes - Class 11 Data Science (844)

Randomization Notes of Class 11 DS covers use of survey, sampling bias, confidence level, data collection using sensors with easy explaination.

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Use of Survey

A survey is a research method used to collect data from people through a questionnaire.
The quality of the survey depends on how the questions are written.
Survey questions should be carefully worded so that they do not hurt the feelings of the respondents.
Surveys include two types of questions: open-ended and close-ended questions.
Open-ended questions allow respondents to answer in their own words.
Examples of open-ended questions include comments/reviews and suggestions for improvement.
Close-ended questions provide fixed answer choices for the respondents.
Examples of close-ended questions include multiple-choice questions, Yes/No questions, rating scales (1–10), and emojis.

Sampling bias occurs when some members of a population have a higher or lower chance of being selected than others.
A biased sample is a non-random sample because every member does not have an equal chance of selection.
Sampling bias can lead to incorrect or misleading results.
To avoid sampling bias, the sample should be selected randomly.
In a random sample, every member of the population has an equal chance of being selected.

The confidence interval is a statistical measure that shows how accurate or reliable an estimate is.
To study a population, a sample is selected because it is often not possible to examine the entire population.
A population parameter is a value that describes the characteristics of the entire population, such as the population mean.
Inference is the process of drawing conclusions about a population based on a sample.
Different samples from the same population may produce different results, causing sampling error.
A confidence interval gives a range within which the actual population parameter is likely to lie.
For example, if the mean weight of mangoes is 250 g with a confidence interval of 20 g, the actual mean is likely to lie within that range.

Variation in the population affects the confidence interval. Greater variation leads to a wider confidence interval, while lower variation leads to a narrower confidence interval.
Sample size also affects the confidence interval. A small sample gives a wider confidence interval, while a large sample gives a narrower and more reliable confidence interval.

Sensors are another method of collecting data with very little human involvement.
A sensor is a device that detects changes in a physical quantity and converts them into signals.
These signals are then converted into a human-readable form.
A mercury thermometer is an example of a sensor, where changes in temperature cause the mercury level to rise or fall.
Sensors can collect data continuously or only when a specific trigger is activated.
Sensor-based data collection can be performed automatically without human intervention, following predefined rules.

The internet is a large source of data with countless websites and web articles.
Data can be collected from the internet using web data scraping, followed by data cleaning and analysis.

Before collecting data, the subject and its characteristics are identified for analysis.
XML (Extensible Markup Language) is used to store and transport data on the internet.
An XML document consists of tags, element names, and element values.
XML has start tags and end tags, with the element value placed between them.
In XML, each tag is called a node, and a node can contain one or more child nodes.
XML makes it easy to store, display, and organize data on web pages.
XML data can be converted into a table format to make analysis and visualization easier.