From Correlation to Causation through stories and math

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Correlation and causation are two concepts that people often mixup in their minds. I must admit that I myself have been guilty about this, and it unlikely that I would ever entirely grow out of it as it is wired deeply into our psychology. Let me use this article to briefly emphasise what the concepts of correlation and causation means, some interesting stories that have emerged from people misunderstanding these concepts and an algorithm that attempts to find causal relationship using correlation information. Here is a story that I heard a professor of mine, Prof. Dr. Ernst-Jan Camiel Wit, tell us during a lecture. There was a school that was involved in a study to see if providing free mid-day meals to students, which they could choose to be subscribed to this or not. At the end of the study, both the students who subscribed to it and did not where tested for different health indicators. It was observed that the students who chose to have meals from the programme had poorer health

How to Create your own Ad Blocker Chrome Extension

Not very long ago, I read an article stating that Google banned advertisement blockers from its stores. There are several websites which does not let you in if you have an Ad blocker extension installed on your browser. I have not investigated on how these websites detect that, nor do I know whether our own version of advertisement blocker would be immune to that. But, isn't it fun to build something like this on our own?

As the first step, I found a random website that has a Google Ad. I right clicked on the Google Ad and clicked on Inspect button.


As I moved up the Elements inspector, I found that the id of the advertisement starts with "google_ads_". Therefore, I opened the console and typed in the following command:
div = document.querySelector('[id^="google_ads_"]')
This selected the div that contained the advertisement. I went ahead and typed in the following command that would remove the div from the page.

div.parentElement.removeChild(div)



In a similar fashion, one can find different patterns in which different advertisements are found. I also found that many-a-times using "google_" instead of "google_ads_" is better. In order to select all the elements that have ids of matching type, let us use querySelectorAll in place of querySelector and use forEach to iterate over all elements.

Let us add these into a Chrome Extension to automate the process. Follow the following procedure for the same:
  1. Create a new folder named adBlocker.
  2. Create two files named 'manifest.json' and 'background.js' respectively.
  3. Insert the following content in manifest.json file:
    {
    "name": "Ad Blocker",
    "description": "Make ads disappear",
    "version": "2.0",
    "permissions": [
    "activeTab"
    ],
    "background": {
    "scripts": ["background.js"],
    "persistent": false
    },
    "browser_action": {
    "default_title": "Make ads disappear"
    },
    "manifest_version": 2
    }
  4. Insert the following content in the background.js file:
    chrome.browserAction.onClicked.addListener(function(tab) {
    chrome.tabs.executeScript({
    code: `

    var divs = document.querySelectorAll('[id^="google_"]');
    divs.forEach(function(div){
    div.parentElement.removeChild(div);
    });

    `;
    });
    });
  5. Open chrome and type in chrome://extensions as URL.
  6. Click to enable Developer Mode, if not already enabled.
  7. Click on Load Unpacked Extension and navigate to the adblocker folder.
  8. Enable the newly loaded extension.


Now whenever you click on the extension, the advertisements of this type disappears. You can follow a similar procedure and create an extension that can remove all kinds of advertisements that are bothering you.


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