This week can mostly be summed up in one word: volatility. Tech stocks, in particular, saw some big swings. The tech-heavy Nasdaq composite fell about 6% between Monday and Thursday but then rebounded more than 2% on Friday. That meant the Nasdaq composite finished the week down over 3%.

High-growth tech stocks saw even more volatility, with many falling by double digit percentages. While some stocks with frothy valuations deserved a correction, the broader-market decline may have also surfaced a few timely opportunities.

Here's a look back at this week's big movers, along with some key takeaways for investors.

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Tech stocks get hit

Many tech stocks were hit hard this week. Big-name companies including Netflix, Alphabet, and Amazon.com, for instance, finished the week down 3.4%, 4.1%, and 5.4%, respectively.

But two stories worth focusing on are Square (NYSE:SQ) and Roku (NASDAQ:ROKU), whose stocks saw outsize losses this week. By the end of the week, Square and Roku were down 10% and 21%, respectively.

These are good examples of the high-growth stocks that were hit particularly hard. Square and Roku have been on a tear over the past 12 months. Even when including this week's pullback, shares of Square are up 125% over the past 12 months, and Roku has risen 156% over the same timeframe.

Some investors, therefore, may be using this broader market sell-off as a reason to take some profits on these outperformers.

Time to buy?

Of course, one of the great things about volatility is the buying opportunities it creates. Several analysts pointed out two notable stocks worth investing in at their lower prices this week.

Square's big sell-off had two analysts telling investors the stock's decline represented a good time to buy.

Canaccord Genuity analyst Michael Graham upgraded Square stock from a "hold" rating to a "buy" and increased his price target on the stock from $60 to $90. Graham cited the company's execution on growing the number of products that are contributing meaningfully to the company's growth as one of the key reasons for his bullishness. 

Meanwhile, Nomura Instinet analyst Dan Dolev, who has a $125 price target on Square stock, said this week's sell-off was an overreaction. The analyst kept his buy rating on the stock.

An analyst covering Microsoft (NASDAQ:MSFT) is similarly bullish on shares now that they're trading lower. Shares were down about 6% this week before the stock recovered some of the decline on Friday. The rebound was driven both by the analyst's price target increase for the stock and the rise in tech stocks overall on Friday. Macquarie analyst Sarah Hindlian upgraded the stock from "neutral" to "outperform" and increased her price target from $106 to $121. She cited the company's momentum with its cloud-computing business, Azure; her optimistic outlook for the company's gaming business; and improving margins as some of the reasons for her optimism.

John Mackey, CEO of Whole Foods Market, an Amazon subsidiary, is a member of The Motley Fool’s board of directors. Suzanne Frey, an executive at Alphabet, is a member of The Motley Fool’s board of directors. Teresa Kersten, an employee of LinkedIn, a Microsoft subsidiary, is a member of The Motley Fool’s board of directors. Daniel Sparks owns shares of Square. The Motley Fool owns shares of and recommends Alphabet (A shares), Alphabet (C shares), Amazon, Netflix, and Square. The Motley Fool has the following options: short January 2019 $80 calls on Square. The Motley Fool has a disclosure policy.