DSS110 DATA COLLECTION AND PRESENTATION

What is the definition of primary data?

Data measured or collected by the investigator or user directly from the source for the first time.

How is secondary data defined in biostatistics?

Data that has already been gathered or compiled by others from published or unpublished sources.

What is considered the primary advantage of collecting primary data over secondary data?

It provides first-hand, information-rich, and highly reliable data for the immediate user.

Why might a researcher prefer to use secondary data collection methods?

They are significantly more inexpensive and easier to collect than primary data.

In primary data collection, which method type deals with factors that can be counted?

Quantitative data collection methods.

Which primary data collection method involves a direct question-and-answer process between an investigator and a respondent?

Interviews.

What specific advantage do interviews offer regarding the structure of questioning?

High flexibility, as questions can be adjusted or changed according to the situation.

How does an 'uncontrolled' observation situation differ from a 'controlled' one?

In uncontrolled situations, the subjects are unaware they are being observed by the researcher.

Which data collection method is designed to provide a broad perspective from large groups across various geographical locations?

Surveys and questionnaires.

How is a focus group distinguished from a standard interview?

It is conducted with a group of people who share a common characteristic to understand their collective thinking.

What distinguishes 'oral histories' from general interviews?

The data collected is linked strictly to a single phenomenon or particular event.

What is a significant challenge when attempting to collect data from government archives?

The data is not always readily available despite being authentic and verifiable.

In data presentation, what is the 'Textual Method'?

Writing findings in a coherent, narrative manner.

What is the primary demerit of using the textual method for data presentation?

The user must read the entire text to obtain a clear picture of the results.

Term: Tabular Method

Definition: A systematic arrangement of information into columns and rows.

How is a 'simple table' defined in the context of data presentation?

A table containing only one property or characteristic, consisting of classes and their frequencies.

What defines a 'complex table' in data presentation?

A table that presents more than one property or characteristic at the same time.

What is the purpose of a Frequency Distribution Table (FDT)?

To show the number of observations contained in each defined class or category.

Where is the 'Caption' typically located in a frequency distribution table?

Directly above the table, containing the table number and title.

What are the four essential parts of a frequency distribution table?

Caption, column header, row header, and body.

Which graphical method is most widely used for presenting quantitative, continuous data?

Histogram.

In a histogram, what does the height of each rectangle represent?

The class frequency.

What is represented on the $X$-axis when drawing a histogram?

The real class boundaries.

What is the key visual difference between a bar chart and a histogram?

Bar charts have constant, fixed spaces between the bars, while histograms have adjacent rectangles.

For what type of data is a bar chart typically used?

Discrete (separated) or qualitative data.

What is the specific purpose of a 'Multiple Bar Chart'?

To facilitate comparison between two or more sets of inter-related data.

Which chart type represents data where the total magnitude is divided into various sub-sections?

Component bar chart.

What defines a 'Line Graph'?

A chart using data points connected by straight lines to show changes over a continuous interval.

How are the sections of a pie chart determined?

According to the percentage of frequencies in each category of the distribution.

What values are plotted along the $X$-axis of a frequency polygon?

Class marks or class midpoints.

What is an 'Ogive'?

A graph showing cumulative frequency plotted against upper or lower class boundaries.

In constructing an ogive, how are the plotted points connected?

By a free-hand curve.

What is a 'Pictogram' (or Pictorial Chart)?

A visual representation of data using icons or pictures in relative sizes to highlight trends.

What is the primary goal of data preprocessing?

To transform raw data into an understandable format suitable for data mining or machine learning.

In data preprocessing, what does the technique of 'sampling' involve?

Selecting a representative subset from a large population of data.

What is the purpose of 'imputation' in data preparation?

Synthesising statistically relevant data to fill in missing values.

The process of removing noise from data during preprocessing is known as _____.

Denoising

What is 'Feature Extraction' in the context of data preprocessing?

Pulling out a significant subset of relevant features for a particular context.

What is the first step in the data preprocessing pipeline?

Data profiling.

What is the main objective of 'Data Profiling'?

To examine and review data to collect statistics about its quality.

Which preprocessing task focuses on eliminating 'bad data' or filling in gaps?

Data cleansing.

Why is 'Data Reduction' necessary for large raw datasets?

To eliminate redundant data that is not relevant to a particular analytical task.

Which preprocessing step involves structuring unstructured data or identifying important ranges?

Data transformation.

What is the intended result of 'Data Enrichment'?

A dataset balanced between training time and required compute power.

In 'Data Validation', into which two sets is the data typically split?

Training data and testing data.

What is the fundamental Python package used for scientific computing and N-dimensional arrays?

NumPy.

Which Python library is specifically designed for high-performance data manipulation and analysis structures?

Pandas.

Which Python library provides a high-level interface for data visualisation based on Matplotlib?

Seaborn.

What risk does a researcher face if missing values are not handled properly?

Drawing inaccurate inferences or obtaining results that differ from the true population.

When replacing a missing numeric value, what three statistical measures are commonly used?

$mean$, $median$, or $mode$.

In the machine learning preprocessing pipeline, what is 'Step 6'?

Feature Scaling.

What is the first step in constructing a statistical graph?

Draw and label the $X$ and $Y$ axes.

How is the width (base) of a rectangle in a histogram determined?

By the class length.

Which chart type is best for showing how values change over time?

Line graph.

What must be determined before a histogram can be drawn from raw data?

The frequency table.

What does 'Normalisation' achieve in data preprocessing?

It organises data for more efficient access.

Which step in machine learning preprocessing involves handling 'Categorical Values'?

Step 4.

What is the purpose of 'Principal Component Analysis' in the context of data reduction?

To transform raw data into a simpler form suitable for specific use cases.

In a frequency polygon, how are the class midpoints connected?

With straight lines.

What determines the percentage of the circle taken up by a category in a pie chart?

The relative frequency of that category.