3 Ways to Hide Your Credentials

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Now that I’m working at a cloud security company, I’ve started to develop a security mindset, and I realize how important it is for us all to play an indispensable role in protecting businesses from cyberattacks. Especially with many of us working from home due to COVID19, cybersecurity is more important than ever before! We really shouldn’t underestimate the power of hackers. Back when I was a teenager, my credentials for social media actually got stolen several times just because I opened an attachment or clicked on a phishing link in an email. …

Lessons Learned From My Job Searching Journey

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My Job Search Journey

I recently started a new job as a Data Scientist at my dream company. A year ago, I was still struggling to get picked for an interview. Never have I ever thought that I will be working at a Fortune 100 company a year later. Honestly, it’s been a roller coaster of a journey, especially as entry-level job postings are down 68% due to the pandemic¹. Now that the job market has opened up a bit, I wanted to share my story, and hopefully, it can help those who are starting their job search journey right now.

A little bit…

Best Resources to Upscale Your Skills and Portfolio

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There are thousands of free courses online. Thanks to the internet, we can now learn almost everything online. However, it’s possible that once you got the course certificates, you may have forgotten what you have learned if you just finished watching all the videos. The best way to learn machine learning or anything is by working on a project. Besides, it’s always great to add another personal project to your GitHub repo. 🙌

If you’re new to data science, you probably don’t know where to start. Don’t worry! Everyone starts somewhere. I still remember myself working on the famous Titanic…

Top SQL Interview Questions You Should Know in 2021

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It’s almost the end of the year! I hope you all are studying hard and doing well. The beginning of the year (January and February) is usually the best time of the year to look for a job. So we need to be better prepared now and hit the ground running in 2021!

Tech companies usually have a large amount of data stored in their relational databases, so they want to see whether the candidates can extract and manipulate data using complex SQL queries before jumping into any modeling. SQL questions can be very tricky, so don’t underestimate SQL. Besides…

A Step-by-Step Guide to Accessing Spotify Data and Creating a
Radar Chart

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It’s almost the end of 2020! If you have been using Spotify for years, you probably know at the end of each year, Spotify will provide premium users personalized insights, such as your favorite songs and artists, and how much time you spent on the services, etc. As a data scientist, I wanted to take a look at all the songs’ audio features from the Discovery Weekly playlist and see what music features I enjoy the most based on my listening history on Spotify.

Setting Up Spotify’s Web API


A Step-by-Step Guide to Setting Up a Cron Job

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Have you ever found yourself doing repetitive tasks on a regular basis? For example, deleting temporary files every week to conserve your disk space, scraping data from a site every week to gather new information or sending recurring emails to the same set of people for “reminder” campaigns, and so on. If so, you might want to set up a cron job scheduler, which will automatically perform the tasks for you at any scheduled time.

Cron comes from “chron,” the Greek prefix for “time.” …


With No Errors

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If you are familiar with the job-hunting process, you probably already noticed that some companies like using take-home assignments to determine if a candidate is the right fit or not. Since most companies use SQL, it’s common that they want to see if you can solve problems using SQL. However, not all the companies will provide you any dataset to work with. It’s likely that a company might only provide a table schema, and you might be wondering if your queries can actually run. Therefore, importing a dataset into a database can be very helpful.

In this article, I will…

Comparison of Supervised and Unsupervised Fraud Detection

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Since Yelp’s early days, reviews are one of the most important factors customers have relied on to determine the quality and authenticity of a business. A local consumer review survey published last year shows that 90% of consumers used the internet to find a local business in the previous year, and 89% of 35–54-year-olds trust online reviews as much as personal recommendations. Although Yelp’s listings often have hundreds or thousands of reviews, many of those reviews can’t be trusted.

“Fake reviews can be devastating to a brand. Simply put, once shoppers suspect a company of having fake reviews, trust is…


A gentle introduction to imputation of missing values

Missing Data
Missing Data
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The biggest challenge for data scientists is probably something that sounds mundane, but very important for any analyses — cleaning dirty data. When you think of dirty data, you are probably thinking about inaccurate or malformed data. But the truth is, missing data is actually the most common occurrence of dirty data. Imagine trying to do a customer segmentation analysis, but 50% of the data have no address on record. It would be hard or impossible to do your analysis since the analysis would be bias in showing no customers in certain areas.

Explore Missing Data

  • How much data is missing? You can…


Four Types of Sampling Methods all Data Scientists Must Know

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Why do we need Sampling?

Sampling is used when we try to draw a conclusion without knowing the population. Population refers to the complete collection of observations we want to study, and a sample is a subset of the target population. Here’s an example. A Gallup poll¹, conducted between July 15 to 31 last year, found that 42% of Americans approve of the way Donald Trump is handling his job as president. The results were based on telephone interviews of a random sample of ~4500 calls (assuming one adult per call. ~4500 adults), aged 18 and older, living in the U.S. The poll was conducted…

👩🏻‍💻 Kessie Zhang

(っ◔◡◔)っ ♥ Data Scientist | 100K+ views | I write about Data Science, Interview Prep, Career and Productivity Tips ♥

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