It's crucial for investors to be in the best-performing mutual funds to suit their investment strategies. TheStreet.com Ratings analyzes mutual funds by investment classes so investors know which ones are performing well -- and which are not.

Below is our recap of the best and worst performers in a variety of open-end mutual fund classifications for the week ending Oct. 4. All total-return figures and stock-price movements were computed over that Wednesday-to-Wednesday period.

Large-Cap

The top-performing large-cap fund was the

(AMDEX) - Get AMIDEX35 Israel E Report

Amidex35 Israel Mutual Fund (AMDEX), which grew 2.9%. Its top holding,

Teva Pharmaceuticals

(TEVA) - Get Teva Pharmaceutical Industries Limited Sponsored ADR Report

, advanced 2.8%. With a drubbing of 5.8% for the

(TAGRX) - Get JHancock Fundmntl Large Cap Core A Report

John Hancock Large-Cap Equity Fund's (TAGRX) largest position of

British Energy Group

(BGY) - Get BlackRock Enhanced International Dividend Trust of Benef Interest Report

on the recent reversal in energy prices, the fund lost 2.4% of its value.

Mid-Cap

The

(AFMAX)

AFBA 5Star Mid Cap Fund (AFMAX) rose 2.2%; its largest holding,

Checkfree

(CKFR)

, moved up 2.1%. The

(ADJEX) - Get Azzad Ethical Report

Azzad Ethical Mid-Cap Fund (ADJEX) fared less well, down 1.3%, as holding

Questar

(STR)

gave up 2.1%.

Small-Cap

The

(BUFSX) - Get Buffalo Small Cap Investor Report

Buffalo Small-Cap Fund (BUFSX) improved by 2.2%, bolstered by a 4.4% bump in

WMS Industries

(WMS) - Get Advanced Drainage Systems, Inc. Report

. On the downside,

(ASTRX)

Ameritor Security Trust Fund (ASTRX) slid 2.7% as its position in Canada's

Northern Dynasty Minerals

(NDM)

was cut by 11.3%.

Aggressive Growth

Insider buying by a

Goodrich

(GR)

director added 2.2% to the stock and 2.1% to the

(HCMAX) - Get Hillman Value Report

Hillman Focused Advantage Fund (HCMAX). The

(NCAPX)

New Century Opportunistic Portfolio (NCAPX), a fund of funds, slipped 1.4% as its largest fund holding,

iShares Goldman Sachs Natural Resources Index Fund

(IGE) - Get iShares North American Natural Resources ETF Report

, gave back 3.4%.

Growth

(NVLCX)

The Wells Fargo Large Company Growth Fund (NVLCX) rose 2.9%; its biggest holding,

eBay

(EBAY) - Get eBay Inc. Report

, skyrocketed 10.3%. On the other hand,

Ceradyne's

(CRDN)

TheStreet Recommends

delinquency in financial reporting cost that company's stock 6.5%, and the

(OBEGX) - Get Oberweis Global Opportunities Inv Report

Oberweis Emerging Growth Fund (OBEGX) 1.9%.

Growth & Income

An appreciation of 3% in

Morgan Stanley

(MS) - Get Morgan Stanley (MS) Report

pushed the

(NEFOX) - Get Natixis Oakmark A Report

IXIS-Harris Associates Large Cap Value Fund (NEFOX) higher by 1.6%. The

(NCCPX)

New Century Capital Portfolio (NCCPX), another fund of funds, fell 1.0% as crude prices pushed down its holding of

iShares Dow Jones US Energy Sector Index Fund

(IYE) - Get iShares U.S. Energy ETF Report

by 2.7%.

Index

The

(RYVYX) - Get Rydex NASDAQ-100 2X Strategy H Report

Rydex Dynamic OTC Fund (RYVYX), which aims to return twice as much as the

Nasdaq 100

, popped 2.7% as

Microsoft

(MSFT) - Get Microsoft Corporation (MSFT) Report

edged 1.8% higher. The Azzad Ethical Mid Cap Fund, which also topped the mid-cap decliners, was down by 1.3% as 4.1% was pumped out of

Noble Energy's

(NBL) - Get Noble Energy, Inc. (NBL) Report

value.

Sector

Pumped by

Google's

(GOOG) - Get Alphabet Inc. Class C Report

3.2% ascent, the

(INPIX) - Get ProFunds Internet UltraSector Inv Report

ProFunds Internet UltraSector ProFund (INPIX) jumped 5.5%. As the Dow Jones Precious Metals Index headed in the other direction by 6.4%, the

(PMPIX) - Get ProFunds Precious Metals Ultra Inv Report

ProFunds Precious Metals UltraSector ProFund (PMPIX), which tracks 150% of the index return, was slashed by 9.6%.

Value

The

(MBOVX) - Get M Funds Inc Business Opport Value Report

Business Opportunity Value Fund (MBOVX) climbed 2.5% with the help of a 3.6% boost engineered by

Biogen Idec

(BIIB) - Get Biogen Inc. Report

. The John Hancock Large-Cap Equity Fund, which was also the large-cap loser, shed 2.4% as its second-largest holding of

Agnico-Eagle Mines

(AEM) - Get Agnico Eagle Mines Limited Report

became 11.4% more undervalued.

Emerging Market

The

(NECAX)

ING Emerging-Countries Fund (NECAX) rose 1.7%, and its top holding of

Partner Communications

(PTNR) - Get Partner Communications Co. Ltd. Sponsored ADR Report

jumped by 6.5%. A 1.7% dip in

Samsung Electronics

helped scrape 0.7% off the Templeton Institutional Fund's

(TEEMX)

Emerging-Markets Series (TEEMX).

Editor's Note: Over a three-year period, funds in sectors tend to move together, but they can diverge greatly in week-to-week performance. As this article focuses on one-week returns, it is not intended to agree with our ratings that examine time periods of as long as three years. Therefore, it is likely that either the winners or losers may disagree with our longer-term outlook. As a fund being up or down in any given week is not a reason to buy or sell that fund, please be sure any potential investment fits your long-term portfolio goals.

Kevin Baker became the senior financial analyst for TSC Ratings upon the August 2006 acquisition of Weiss Ratings by TheStreet.com, covering mutual funds. He joined the Weiss Group in 1997 as a banking and brokerage analyst. In 1999, he created the Weiss Group's first ratings to gauge the level of risk in U.S. equities. Baker received a B.S. degree in management from Rensselaer Polytechnic Institute and an M.B.A. with a finance specialization from Nova Southeastern University.