Sampling Basics and Objectives (2021)

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In this article, we will discuss the Sampling Basics. It is often required to collect information from the data. These two methods are used for collecting the required information.

  • Complete information
  • Sampling

Complete Information

This method collects the required information from every individual in the population. This method is used when it is difficult to draw some conclusion (inference) about the population based on sample information. This method is costly and time-consuming. This method of getting data is also called Complete Enumeration or Population Census.

Sampling Basics

What is Sampling?

Sampling is the most common and widely used method of collecting information. Instead of studying the whole population only a small part of the population is selected and studied and the result is applied to the whole population. For example, a cotton dealer picked up a small quantity of cotton from the different bales to know the quality of the cotton.

Sampling and Sampling Distribution

Purpose or objective of sampling

Two basic purposes of sampling are

  1. To obtain the maximum information about the population without examining every unit of the population.
  2. To find the reliability of the estimates derived from the sample, which can be done by computing the standard error of the statistic.

Advantages of sampling over Complete Enumeration

  1. It is a much cheaper method to collect the required information from the sample as compared to complete enumeration as fewer units are studied in the sample rather than the population.
  2. From a sample, the data can be collected more quickly and greatly save time.
  3. Planning for sample surveys can be done more carefully and easily as compared to complete enumeration.
  4. Sampling is the only available method of collecting the required information when the population object/ subject or individual in the population is destructive.
  5. Sampling is the only available method of collecting the required information when the population is infinite or large enough.
  6. The most important advantage of sampling is that it provides the reliability of the estimates.
  7. Sampling is extensively used to obtain some of the census information.
Sampling Basics and Objectives

This is all about Sampling Basics.

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For further reading visit: 

Sampling Theory and Reasons to Sample
Sampling Basics

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The Spearman Rank Correlation Test (Numerical Example)

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Consider the following data for the illustration of the detection of heteroscedasticity using the Spearman Rank correlation test. The Data file is available to download.

YX2X3
11208.1
16188.4
11228.5
14218.5
13278.8
17269
14258.9
15279.4
12309.5
18289.5

The estimated multiple linear regression model is:

$$Y_i = -34.936 -0.75X_{2i} + 7.611X_{3i}$$

The Residuals with the data table are:

YX2X3Residuals
11208.1-0.63302
16188.40.575564
11228.5-2.16954
14218.50.076455
13278.81.317102
172693.040825
14258.90.047951
15279.4-1.2497
12309.5-2.74881
18289.51.743171

We need to find the rank of absolute values of $u_i$ and the expected heteroscedastic variable $X_2$.

$Y$$X_2$$X_3$ResidualsRank of |$u_i$|Rank of $X_2$$d$$d^2$
11208.1-0.633 4224
16188.40.576 3124
11228.5-2.170 84416
14218.50.076 23-11
13278.81.317 67.5-1.52.25
172693.041 106416
14258.90.048 15-416
15279.4-1.250 57.5-2.56.25
12309.5-2.749 910-11
18289.51.743 79-24
       Total =070.5

Calculating the Spearman Rank correlation

\begin{align}
r_s&=1-\frac{6\sum d^2}{n(n-1)}\\
&=1-\frac{6\times 70.5)}{10(100-1)}=0.5727
\end{align}

Let us perform the statistical significance of $r_s$ by t-test

\begin{align}
t&=\frac{r_s \sqrt{n}}{\sqrt{1-r_s^2}}\\
&=\frac{0.5727\sqrt{8}}{\sqrt{1-(0.573)^2}}=1.977
\end{align}

The value of $t$ from the table at a 5% level of significance at 8 degrees of freedom is 2.306.

Since $t_{cal} \ngtr t_{tab}$, there is no evidence of the systematic relationship between the explanatory variables, $X_2$ and the absolute value of the residuals ($|u_i|$) and hence there is no evidence of heteroscedasticity.

Since there is more than one regressor (the example is from the multiple regression model), therefore, Spearman’s Rank Correlation test should be repeated for each of the explanatory variables.

Spearman Rank Correlation

As an assignment perform the Spearman Rank Correlation between |$u_i$| and $X_3$  for the data above. Test the statistical significance of the coefficient in the above manner to explore evidence about heteroscedasticity.

Read about Pearson’s Correlation Coefficient

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How to Fix Instagram Story Video Quality Blurry Problem

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The quality of your video is too bad after uploading to Instagram Story? In this article, we will tell you why the video on Instagram Story is blurry, and how to fix Instagram story video quality.

FlexClip: Fix Instagram Story Video Quality

If you are a longtime Instagram user, you will realize the importance of video/ photo quality on Instagram. However, on social networks, you see a lot of people complaining about topics like this.

“My videos became of poor quality after uploading them to Instagram. There is no problem with the video. Why and how do I fix this problem? ”

Poor quality video on Instagram Stories can occur for many reasons, including Internet connection, and app version. Whatever it is, the problem of poor-quality Instagram story videos is not difficult to solve. Follow the methods below and say no to blurred Instagram video stories. The methods below can be used to fix Instagram story video quality.

Ways to Fix Instagram Story Video Quality Problem

1. Check Internet connection

If your Internet connection is unstable, uploaded Instagram videos may be blurred because they have not been fully loaded. While you are uploading a video to Instagram with a poor Internet connection, Instagram will automatically reduce the quality of the video for upload. Try to connect your device with a stable WIFI adapter to mobile data.

2. Try different videos and images

Recovered your phone from a backup? Try a different video or photo. The clarity of photos and videos can change in the damaged backup.

3. Reset network settings

On an iPhone, to reset network settings, you have to go to Settings> General> Reset> Reset Network Settings. On an Android phone, you need to go to Settings> Backup and reset> Reset Network Settings.

4. Adjust camera settings

When your phone is unable to record high-quality video, here’s what you do to adjust your phone camera settings.

On Android:

Step 1:  Open the default Camera app on your phone.

Step 2:  Click the Settings icon shaped like a gear icon.

Step 3:  Adjust the image and video size to the highest quality.

On iPhone:

Step 1  Launch the iPhone Settings app on your phone.

Step 2  Find Camera.

Step 3  Adjust camera quality and turn on “Automatic DHR”.

5. Picture and video size is not the correct aspect ratio

Instagram limits the size and quality of the photos and videos you upload. If you’re uploading a video or photo that’s too large, Instagram compresses it so your video loads faster. One solution is to not use the phone’s camera. Use Instagram’s camera instead. No cuts and no quality loss.

6. Update the application

When you’re on an older version of Instagram, Instagram Story videos may appear worse. Update it so you can enjoy your new Instagram journey.

7. Adjust Instagram settings

Instagram burns your mobile data. To prevent you from misusing your data, Instagram gives you a setting to keep your mobile data usage to a minimum. This will dramatically decrease the quality of your Instagram feed. Here’s what you do to disable this setting.

Step 1:  Launch Instagram and tap on your profile icon.

Step 2:  Click on the three horizontal lines.

Step 3:  Go to Settings> Accounts> Cellular Data Usage.

Step 4:  Turn off Data Saver.

8. Use a photo/video editing app

Instagram has certain requirements for videos and photos. If the video you want to upload doesn’t meet the requirements, Instagram will automatically trim or compress it.

Lots of video editors like FlexClip help you crop and compress videos to fit Instagram story format without losing video quality. In clicks, you can adjust the aspect ratio, video length, and video size.

Moreover, it also gives you other video editing tools for video upscaling, like transitions, filters, and video speed changers. Last but not least, FlexClip has a ton of media resources that you can apply, including video clips, photos, music, and even royalty-free pre-made video templates.

FlexClip: Fix Instagram Story Video

Conclude

With 8 solutions to poor-quality video processing on Instagram stories, you will no longer experience blurred Instagram video stories! Share this post if you found it helpful to fix Instagram story video quality.

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